workflows: Run pull_request_target for differnt context

As suggested in similar actions: https://github.com/actions/labeler

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

Author: nuclearcat

.github/workflows/main.yml

@@ -7,7 +7,7 @@ on:
   # Triggers the workflow on push or pull request events but only for the main branch
   push:
     branches: [ main ]
-  pull_request:
+  pull_request_target:
     branches: [ main ]
 
   # Allows you to run this workflow manually from the Actions tab
@@ -49,7 +49,7 @@ jobs:
         run: |
           python tests/validate_yaml.py
   on-fail:
-    if: failure() && github.event_name == 'pull_request'
+    if: failure() && github.event_name == 'pull_request_target'
     runs-on: ubuntu-latest
     needs: check
     permissions: