Rename index.md to _index.md for compatibility with docs-gitlab-com

...javascripts/ci/catalog/components/list/catalog_header.vue

...ts/ci/catalog/components/shared/ci_verification_badge.vue

app/assets/javascripts/ci/catalog/constants.js

...ipts/ci/pipeline_details/manual_variables/empty_state.vue

...ripts/environments/components/enable_review_app_modal.vue

...sets/javascripts/google_cloud/databases/service_table.vue

...sets/javascripts/ide/components/pipelines/empty_state.vue

...cts/shared/permissions/components/ci_catalog_settings.vue

app/assets/javascripts/releases/components/app_index.vue

...rge_request_widget/components/states/nothing_to_merge.vue

app/helpers/ci/pipeline_editor_helper.rb

app/helpers/ide_helper.rb

app/presenters/dev_ops_report/metric_presenter.rb

app/presenters/projects/security/configuration_presenter.rb

app/views/projects/settings/ci_cd/_form.html.haml

app/views/projects/settings/ci_cd/show.html.haml

app/views/protected_branches/shared/_index.html.haml

...istration/backup_restore/troubleshooting_backup_gitlab.md

doc/administration/dedicated/hosted_runners.md

doc/administration/geo/replication/datatypes.md