Add migration to drop snippet_repositories.shard_id NOT NULL constraint
What does this MR do and why?
Add migration to drop snippet_repositories.shard_id NOT NULL constraint
This is part of the cells work to shard this table by organization_id.
Changelog: added
Database migration output
be rake db:migrate
main: == [advisory_lock_connection] object_id: 130260, pg_backend_pid: 6078
main: == 20251021184052 RemoveNotNullConstraintFromSnippetRepositoriesShard: migrating
main: -- change_column_null(:snippet_repositories, :shard_id, true, nil)
main: -> 0.0313s
main: == 20251021184052 RemoveNotNullConstraintFromSnippetRepositoriesShard: migrated (0.0539s)
main: == [advisory_lock_connection] object_id: 130260, pg_backend_pid: 6078
ci: == [advisory_lock_connection] object_id: 130260, pg_backend_pid: 6079
ci: == 20251021184052 RemoveNotNullConstraintFromSnippetRepositoriesShard: migrating
ci: -- change_column_null(:snippet_repositories, :shard_id, true, nil)
ci: -> 0.0045s
ci: == 20251021184052 RemoveNotNullConstraintFromSnippetRepositoriesShard: migrated (0.0132s)
ci: == [advisory_lock_connection] object_id: 130260, pg_backend_pid: 6079
Related to #577964