Specifically check origin

.github/workflows/lint.yml

@@ -64,7 +64,7 @@ jobs:
         # Womtool validate checks very slowly, so this saves a lot of time.
         run: |
           bash -c '
-            for WDL_FILE in $(git diff --name-only ${{github.base_ref}} | grep -E '*.wdl$'); do
+            for WDL_FILE in $(git diff --name-only origin/${{github.base_ref}} | grep -E '*.wdl$'); do
               womtool validate $WDL_FILE
             done
           '