Enforce trailing comma in JS on multiline (#30002)

To keep blame info accurate and to avoid [changes like
this](https://github.com/go-gitea/gitea/pull/29977/files#diff-c3422631a14edbe1e508c4b22f0c718db318be08a6e889427802f9b6165d88d6R359),
it's good to always have a trailing comma, so let's enforce it in JS.

This rule is completely automatically fixable with `make lint-js-fix`
and that's what I did here.

web_src/js/components/PullRequestMergeForm.vue

@@ -43,7 +43,7 @@ export default {
       for (const elem of document.querySelectorAll('[data-pull-merge-style]')) {
         toggleElem(elem, elem.getAttribute('data-pull-merge-style') === val);
       }
-    }
+    },
   },
   created() {
     this.mergeStyleAllowedCount = this.mergeForm.mergeStyles.reduce((v, msd) => v + (msd.allowed ? 1 : 0), 0);