Non-sense "You pushed on branch ...." notification

[wxiaoguang]

Description

Reproduce step:

1. Create a branch
2. Create a PR
3. Merge the PR
4. Go to the repo home

Now, these 2 notifications are non-sense.

• For "main" branch: yes, it is changed.
• For "root-patch-1": it has been merged.

Gitea Version

1.21

[silverwind]

Default branch should never notify imho.

[hiifong]

Default branch should never notify imho.

agree

[dsseng]

I want to work on this. If I won't submit a fix within a week, consider the task free again

[dsseng]

Oops, apparently lunny also took this, but only made it ignore default branch. My PR does also exclude branches with merged PRs. Let me rebase it