danger-review: Make image configurable

What does this MR do?

Allow configuration of image for danger-review via DANGER_IMAGE variable.

This simplifies customizing the needed image. For example: gitlab-org/release-tools!2728 (merged).

Usage:

include:
  - project: 'gitlab-org/quality/pipeline-common'
    file:
      - '/ci/danger-review.yml'

danger-review:
  variables:
    DANGER_IMAGE: ruby:3.3

For example: gitlab-org/release-tools!2728 (merged)

Check-list

• Ensure commits include Changelog: trailer
• Verify the change in all affected pipelines.