cicd: allow deploy-docs to trigger from comments

Signed-off-by: Hank Donnay <hdonnay@redhat.com>
Change-Id: Ic8dc5f62f620dc8b5320d9b2b5b49f846a6a6964

Author: hdonnay

.github/workflows/fast-forward.yml

@@ -31,7 +31,7 @@ jobs:
           merge: true
           comment: on-error
   deploy-docs:
-    if: ${{ success() && github.base_ref == 'main' }}
+    if: ${{ success() && github.event.issue.pull_request }}
     permissions:
       contents: write
     needs: fast-forward