Update diffcalc workflow

.github/workflows/diffcalc.yml

@@ -110,10 +110,14 @@ jobs:
     if: ${{ github.event_name == 'workflow_dispatch' || contains(github.event.comment.body, '!diffcalc') }}
     steps:
       - name: Check permissions
-        if: ${{ github.event_name != 'workflow_dispatch' }}
-        uses: actions-cool/check-user-permission@a0668c9aec87f3875fc56170b6452a453e9dd819 # v2.2.0
-        with:
-          require: 'write'
+        run: |
+          ALLOWED_USERS=(smoogipoo peppy bdach)
+          for i in "${ALLOWED_USERS[@]}"; do
+              if [[ "${{ github.actor }}" == "$i" ]]; then
+                  exit 0
+              fi
+          done
+          exit 1
 
   create-comment:
     name: Create PR comment