Only update GithubRepos once in RepoSyncWorker (#14175)

Touching the GithubRepo invokes GithubRepo#clear_caches, so calling
`update` and then `touch` calls `clear_caches` *twice*. This pulls it
back to calling it once.

app/workers/github_repos/repo_sync_worker.rb

@@ -27,8 +27,10 @@ module GithubRepos
           watchers_count: fetched_repo.watchers,
           stargazers_count: fetched_repo.stargazers_count,
           info_hash: fetched_repo.to_hash,
+          # Touch `updated_at` even if nothing here was updated. See PR #12853
+          # for more details.
+          updated_at: Time.current,
         )
-        repo.touch(:updated_at)
         if repo.user&.github_repos_updated_at&.before?(TOUCH_USER_COOLDOWN.ago)
           repo.user.touch(:github_repos_updated_at)
         end