Backport #24825 by @yardenshoham
The topics are saved in the repo_topic table with a repoID key. They are
also saved directly in the repository table.
Before this PR, only `AddTopic` and `SaveTopics` made sure the `topics`
field in the repository field was synced with the repo_topic table.
This PR makes sure `GenerateTopics` and `DeleteTopic` also sync the
`topics` in the repository table.
`RemoveTopicsFromRepo` doesn't need to sync the data as it is only used
to delete a repository.
- Fixes#24820
04f9ab1aa9