[v12.0/forgejo] fix: redirect from /{username}/{reponame}/pulls/{index} to issue if index is a issue (#8876)

**Backport:** !8874

conflict resolved by accepting the incomming hunk and removing TestIssueTimelineLabels-func

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8876
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Reviewed-by: floss4good <floss4good@noreply.codeberg.org>
Co-authored-by: zokki <zokki.softwareschmiede@gmail.com>
Co-committed-by: zokki <zokki.softwareschmiede@gmail.com>

routers/web/repo/pull.go

@@ -360,7 +360,7 @@ func getPullInfo(ctx *context.Context) (issue *issues_model.Issue, ok bool) {
 	ctx.Data["Issue"] = issue
 
 	if !issue.IsPull {
-		ctx.NotFound("ViewPullCommits", nil)
+		ctx.Redirect(issue.Link())
 		return nil, false
 	}