Automation: remove 'Waiting for Author' label in more cases (#2802)

Namely when a PR review comment is made by the author, which
for some reason is treated separately from 'top level' PR
comments.

Author: fingolfin

.github/workflows/labels.yml

@@ -3,6 +3,8 @@ name: Update Status Labels When Author Replies
 on:
   issue_comment:
     types: [created]
+  pull_request_review_comment:
+    types: [created]
 
 permissions:
   issues: write