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/features/repo-code.js

@@ -116,7 +116,7 @@ function showLineButton() {
       tippy.popper.addEventListener('click', () => {
         tippy.hide();
       }, {once: true});
-    }
+    },
   });
 }