api: GetPullRequestCommits: return file list (#27483)

Fixes https://github.com/go-gitea/gitea/issues/27481

----

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/api_repo_git_notes_test.go

@@ -37,5 +37,7 @@ func TestAPIReposGitNotes(t *testing.T) {
 		var apiData api.Note
 		DecodeJSON(t, resp, &apiData)
 		assert.Equal(t, "This is a test note\n", apiData.Message)
+		assert.NotEmpty(t, apiData.Commit.Files)
+		assert.NotNil(t, apiData.Commit.RepoCommit.Verification)
 	})
 }