Don't use branch main

Author: simonw

.github/workflows/deploy-demo.yml

@@ -107,7 +107,6 @@ jobs:
         datasette publish cloudrun github.db \
             -m demo-metadata.json \
             --service github-to-sqlite \
-            --branch=main \
             --install=datasette-search-all>=0.3 \
             --install=datasette-render-markdown>=1.1.2 \
             --install=datasette-pretty-json>=0.2.2 \