chore: delete greeting on first user issue/post

Author: woothu

.github/workflows/greetings.yml

@@ -1,6 +1,6 @@
 name: Greetings
 
-on: [pull_request, issues]
+on: [pull_request]
 
 jobs:
   greeting:
@@ -9,5 +9,5 @@ jobs:
     - uses: actions/first-interaction@v1
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
-        issue-message: 'Hi! Thank you for your first contribution to our project. You are helping to make our product better! :)'
+        issue-message: 'Hi! Thank you for your first contribution to our project. :)'
         pr-message: 'Hi! Thank you for your first PR to our project. You are helping to make our product better! :)'