remove debugging print and only publish on main branch

.github/workflows/build.yml

@@ -2,13 +2,13 @@ name: ci
 
 on:
   push:
+    branches:
+      main
 
 jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
-      - name: Blah
-        run: echo ${{ github.server_url }}/${{ github.repository }}
       - name: Login to Docker Hub
         uses: docker/login-action@v3
         with: