Fix workflow check by making grep quiet

Author: albhilazo

.github/workflows/generate-pdf.yml

@@ -21,10 +21,9 @@ jobs:
       - name: Check PDF missing in commit
         id: check-pdf-missing
         run: |
-          pdf_missing=$(git show --name-status --pretty="" | grep "\.pdf$" \
-            && echo 'false' \
-            || echo 'true')
-          echo $pdf_missing
+          git show --name-status --pretty="" | grep -q "\.pdf$" \
+            && pdf_missing='false' \
+            || pdf_missing='true'
           echo "pdf_missing=${pdf_missing}" >> "$GITHUB_OUTPUT"
 
   generate-pdf: