Fix Actions pull_request.paths being triggered incorrectly by rebase (#36045)

Partially fix #34710 

The bug described in #34710 can be divided into two parts: `push.paths`
and `pull_request.paths`. This PR fixes the issue related to
`pull_request.paths`. The root cause is that the check for whether the
workflow can be triggered happens **before** updating the PR’s merge
base. This causes the file-change detection to use the old merge base.
Therefore, we need to update the merge base first and then check whether
the workflow can be triggered.

services/pull/review.go

@@ -333,7 +333,7 @@ func SubmitReview(ctx context.Context, doer *user_model.User, gitRepo *git.Repos
 		if headCommitID == commitID {
 			stale = false
 		} else {
-			stale, err = checkIfPRContentChanged(ctx, pr, commitID, headCommitID)
+			stale, _, err = checkIfPRContentChanged(ctx, pr, commitID, headCommitID)
 			if err != nil {
 				return nil, nil, err
 			}