Change gitlab-runner image to just gitlab/gitlab-runner

The alpine-bleeding tag was not working for me. I was getting this output in my CI jobs:

Using Docker executor with image busybox:latest ...
Pulling docker image registry.gitlab.com/gitlab-org/gitlab-runner/gitlab-runner-helper:x86_64-6e602edd ...
WARNING: Failed to pull image with policy "always": Error response from daemon: manifest for registry.gitlab.com/gitlab-org/gitlab-runner/gitlab-runner-helper:x86_64-6e602edd not found: manifest unknown: manifest unknown (manager.go:203:1s)
ERROR: Job failed: failed to pull image "registry.gitlab.com/gitlab-org/gitlab-runner/gitlab-runner-helper:x86_64-6e602edd" with specified policies [always]: Error response from daemon: manifest for registry.gitlab.com/gitlab-org/gitlab-runner/gitlab-runner-helper:x86_64-6e602edd not found: manifest unknown: manifest unknown (manager.go:203:1s)

I'm not sure if this is working for other people but I was able to fix the problem by switching to the default tag for gitlab/gitlab-runner which matches the example at https://docs.gitlab.com/runner/install/docker.html .