Replace workaround for interruptible jobs with rules

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What does this merge request do and why?

Removes extra stage and extra job that exist as a workaround to make branch jobs interruptible.

From 16.10 it is possible to get the same effect with rules. gitlab!144687 (merged)

How to validate

1. Commit here
2. Commit again while pipeline is running
3. Ensure pipeline is cancelled

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4. Push a tag from another branch
5. Commit again on the same ref

I am not sure if adding tag exception makes sense.

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

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 an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.