ammend output check to work with nice formatting

.github/workflows/terraform-validate.yml

@@ -70,7 +70,7 @@ jobs:
 
     - name: Check built-in functions usage
       run: |
-        if ! grep -q 'upper(' *.tf || ! grep -q 'join(' *.tf || ! grep -Eq '\[for.*:' *.tf; then
+        if ! grep -q 'upper(' *.tf || ! grep -q 'join(' *.tf || ! grep -Eq '\[\s*for.*:' *.tf; then
           echo "Required built-in functions not used correctly!"
           exit 1
         fi