Refactor migration docs

Use strings around milestones so YAML.load_file does not convert
to numerics

ee/elastic/docs/20230702000000_backfill_existing_group_wiki.yml

@@ -3,7 +3,7 @@ name: BackfillExistingGroupWiki
 version: '20230702000000'
 description: BackfillExistingGroupWiki
 group: group::global search
-milestone: 16.2
+milestone: '16.2'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/122529
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230703112233_reindex_commits_to_fix_permissions.yml

@@ -3,7 +3,7 @@ name: ReindexCommitsToFixPermissions
 version: '20230703112233'
 description: ReindexCommitsToFixPermissions
 group: group::global search
-milestone: 16.2
+milestone: '16.2'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125154
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230710142700_add_archived_to_merge_requests.yml

@@ -3,7 +3,7 @@ name: AddArchivedToMergeRequests
 version: '20230710142700'
 description: Adds archvied (boolean) to the merge request index mapping
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126024
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230711140500_backfill_archived_on_merge_requests.yml

@@ -3,7 +3,7 @@ name: BackfillArchivedOnMergeRequests
 version: '20230711140500'
 description: Backfills archived for merge request documents
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126024
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230717132609_backfill_archived_on_work_items.yml

@@ -3,7 +3,7 @@ name: BackfillArchivedOnWorkItems
 version: '20230717132609'
 description: BackfillArchivedOnWorkItems
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126714
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230719094243_add_archived_to_commits.yml

@@ -3,7 +3,7 @@ name: AddArchivedToCommits
 version: '20230719094243'
 description: Add archived column in commit index
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127004
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230719142200_add_archived_to_notes.yml

@@ -3,7 +3,7 @@ name: AddArchivedToNotes
 version: '20230719142200'
 description: Adds the boolean archived field on notes index
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126990
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230719144243_add_archived_to_main_index.yml

@@ -3,7 +3,7 @@ name: AddArchivedToMainIndex
 version: '20230719144243'
 description: Add archived column in main index
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127008
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230719211400_add_archived_to_wikis.yml

@@ -3,7 +3,7 @@ name: AddArchivedToWikis
 version: '20230719211400'
 description: Adds the boolean archived field on wikis index
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126157
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230720000000_reindex_wikis_to_fix_routing.yml

@@ -3,7 +3,7 @@ name: ReindexWikisToFixRouting
 version: '20230720000000'
 description: Change the wiki docs routing from project_{id} or group_{id} to n_{id}
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125137
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230724070100_backfill_epics.yml

@@ -3,7 +3,7 @@ name: BackfillEpics
 version: '20230724070100'
 description: Backfills all epics into Elasticsearch
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125663
 obsolete: false
 marked_obsolete_by_url:

ee/elastic/docs/20230726094700_remove_projects_from_main_index.yml

@@ -3,7 +3,7 @@ name: RemoveProjectsFromMainIndex
 version: '20230726094700'
 description: Remove Project documents from main index.
 group: group::global search
-milestone: 16.3
+milestone: '16.3'
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127002
 obsolete: false
 marked_obsolete_by_url:

scripts/elastic-migration

@@ -151,7 +151,7 @@ end
       'version' => timestamp,
       'description' => options.description,
       'group' => "group::#{options.group}",
-      'milestone' => options.milestone,
+      'milestone' => options.milestone.to_s,
       'introduced_by_url' => options.introduced_by_url,
       'obsolete' => false,
       'marked_obsolete_by_url' => nil,