Run gitpod-docker-image verify job after the image is built

What does this Merge Request do and why?

This MR is a follow-up MR for !2664 (merged). This change updates the rule of gitpod-docker-image verify job to:

• Run this job after build-gitpod-workspace-image job
• Run this job only when the below changes are introduced or on the scheduled pipeline

- "support/ci/verify-gitpod-docker-image"
- "support/gitpod/**/*"

Testing

Tested by making support/gitpod/**/* file change in !2694 (closed) and verified that build-gitpod-workspace-image and gitpod-docker-image job succeeded in https://gitlab.com/gitlab-org/gitlab-development-kit/-/pipelines/598673350

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.