fix: stop notifying draft PRs

Signed-off-by: Varsha GS <varsha.gs@ibm.com>

Author: GSVarsha

.github/workflows/opened-pr-notification-on-slack.yml

@@ -6,7 +6,7 @@ permissions:
 
 on:
   pull_request:
-    types: [opened, reopened]
+    types: [reopened, ready_for_review, review_requested]
 
 jobs:
   notify-slack: