chore: run label based jobs on other events

It seems that Github Actions is not running these jobs even once even
though the PRs are labelled at least once. This patch runs these jobs
on other related PR activity.

.github/workflows/label-check.yml

@@ -1,7 +1,7 @@
 name: Pull Request Label Checker
 on:
   pull_request:
-    types: [labeled, unlabeled]
+    types: [opened, edited, synchronize, labeled, unlabeled]
 jobs:
   check-labels:
     name: prevent merge labels