CI: Use default behavior of update-container-description-action

Previously, we always used README.md as the readme to push as
container description. By not explicitly specifying this file name, we
use the default behavior of the action, which is to push
README-containers.md if it exist, and push README.md otherwise.

In short, nothing will directly change with this commit, but now
repositories can provide a README-containers.md if they want to push a
different README as the container description.

Signed-off-by: beorn7 <beorn@grafana.com>

.github/workflows/container_description.yml

@@ -4,6 +4,7 @@ on:
   push:
     paths:
       - "README.md"
+      - "README-containers.md"
       - ".github/workflows/container_description.yml"
     branches: [ main, master ]
 
@@ -29,7 +30,6 @@ jobs:
           destination_container_repo: ${{ env.DOCKER_REPO_NAME }}
           provider: dockerhub
           short_description: ${{ env.DOCKER_REPO_NAME }}
-          readme_file: 'README.md'
 
   PushQuayIoReadme:
     runs-on: ubuntu-latest
@@ -49,4 +49,3 @@ jobs:
         with:
           destination_container_repo: ${{ env.DOCKER_REPO_NAME }}
           provider: quay
-          readme_file: 'README.md'