ci: Only report flaky tests on master

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab-ci.yml

@@ -40,12 +40,12 @@ default:
   OMNIBUS_GITLAB_CACHE_EDITION: "GITLAB_RUBY3_2"
 
 .default-branch-pipeline-failure-variables: &default-branch-pipeline-failure-variables
+  CREATE_RAILS_FLAKY_TEST_ISSUES: "true"
   CREATE_RAILS_SLOW_TEST_ISSUES: "true"
   CREATE_RAILS_TEST_FAILURE_ISSUES: "true"
 
 .default-merge-request-variables: &default-merge-request-variables
   ADD_SLOW_TEST_NOTE_TO_MERGE_REQUEST: "true"
-  CREATE_RAILS_FLAKY_TEST_ISSUES: "true"
 
 .if-merge-request-security-canonical-sync: &if-merge-request-security-canonical-sync
   if: '$CI_MERGE_REQUEST_SOURCE_PROJECT_PATH == "gitlab-org/security/gitlab" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_DEFAULT_BRANCH && $CI_MERGE_REQUEST_TARGET_BRANCH_NAME == $CI_DEFAULT_BRANCH'