Skipped test building of docker image on push (#1833)

The image will actually get built (and published) anyway.

Author: bmispelon

.github/workflows/docker-test-build.yml

@@ -2,9 +2,6 @@ name: Docker test build
 
 on:
     pull_request:
-    push:
-        branches:
-            - main
 
 concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}