github webhook: Ignore more pull_request actions.

See https://github.com/zulip/zulip/issues/16258 for
possible follow up here.

We now ignore the following two new pull_request
actions (as well as the three existing ones
from before):

    approved
    converted_to_draft

As the issue above indicates, we may want to actually
support "approved" if we can find somebody to work
on the webhook.  (And then the issue goes a little
broader than what changed here.)

zerver/webhooks/github/tests.py

@@ -358,6 +358,8 @@ A temporary team so that I can get some webhook fixtures!
 
     def test_ignored_pull_request_actions(self) -> None:
         ignored_actions = [
+            "approved",
+            "converted_to_draft",
             "labeled",
             "review_request_removed",
             "unlabeled",

zerver/webhooks/github/view.py

@@ -526,6 +526,14 @@ IGNORED_EVENTS = [
     "repository_vulnerability_alert",
 ]
 
+IGNORED_PULL_REQUEST_ACTIONS = [
+    "approved",
+    "converted_to_draft",
+    "labeled",
+    "review_request_removed",
+    "unlabeled",
+]
+
 @api_key_only_webhook_view('GitHub', notify_bot_owner_on_invalid_json=True)
 @has_request_variables
 def api_github_webhook(
@@ -561,8 +569,7 @@ def get_event(request: HttpRequest, payload: Dict[str, Any], branches: Optional[
             return f'{event}_{action}'
         if action == 'ready_for_review':
             return 'pull_request_ready_for_review'
-        # Unsupported pull_request events
+        if action in IGNORED_PULL_REQUEST_ACTIONS:
-        if action in ('labeled', 'unlabeled', 'review_request_removed'):
             return None
     elif event == 'push':
         if is_commit_push_event(payload):