Add missing quote

Author: Bisaloo

.github/workflows/main.yml

@@ -57,5 +57,5 @@ jobs:
       - uses: r-lib/actions/check-r-package@v2
         with:
           upload-snapshots: true
-          build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")
+          build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'