Modify doc check workflow triggers

Author: tarek-y-ismail

.github/workflows/automatic-doc-checks.yml

@@ -2,17 +2,14 @@ name: Main Documentation Checks
 
 on:
   - push
-  - pull_request
   - workflow_dispatch
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true  
+  cancel-in-progress: true
 
 jobs:
   documentation-checks:
     uses: canonical/documentation-workflows/.github/workflows/documentation-checks.yaml@main
-    env:
-      CI: 1
     with:
       working-directory: doc/sphinx