fix: use runner to start activitylog service

activitylog was still using oklog run.Group{} for starting the service
this cause issue during shutdown. Seems this service was overlooked
when switching all the other services to use runner.

Fixes: #2746
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Internal Server Error - Gitea: Git with a cup of tea
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Gitea Version: 1.28.0+dev-477-g8b6ad49a5f