The topics are saved in the `repo_topic` table.
They are also saved directly in the `repository` table.
Before this PR, only `AddTopic` and `SaveTopics` made sure the `topics`
field in the `repository` table 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