Don't rerun the tests when the PR description is edited

Most of the time it's useless and just clogs up the build queue. When it's
useful (e.g. when removing "[Dependent]" from the title), it's easy enough to
retrigger the build manually by updating your branch.

.github/workflows/main.yml

@@ -5,7 +5,7 @@ on:
       - 'master'
       - 'develop'
   pull_request:
-    types: [edited, ready_for_review, opened, synchronize, reopened]
+    types: [ready_for_review, opened, synchronize, reopened]
     paths-ignore:
       - 'site/**'
       - '**/*.md'