reduce commit count in repo view to 5~3 #4647

I don't think we need that many commits in repo index view. GitHub, GitLab and forgejo show just one and I haven't find it problematic. I still have commits page for full commit list.

Even notification toolbar shows max 5, so 10 preview commits there is just too much. Branches and tags are more important than commits. 10 rows of commits burdening branches and tags under scroll doesn't make much sense.

cc @oppi.li @eti.tf