rename default_branch var

Author: plowsof

.github/workflows/download-hashes.yml

@@ -458,7 +458,7 @@ jobs:
           git push --set-upstream origin "$BRANCH_NAME"
 
           gh pr create \
-            --base "$DEFAULT_BRANCH" \
+            --base "$BASE_BRANCH" \
             --head "$BRANCH_NAME" \
             --title "Update Core download information (CLI ${version_cli}, GUI ${version_gui})" \
             --body "This PR was automatically generated by the Download Hashes workflow to update **src/data/downloads/core.json** based on the latest downloads/hashes.txt."