Stop running CI on linux-cip tags

Issue description

Currently we run through our CI pipeline for all pushes made to the linux-cip GitLab repository. This includes both branches and tags.

As tags are always made from our branches, i.e. there are no orphan tags, this ends up with us running CI on code that has already had CI run on it, wasting resources.

Let's stop running our CI pipeline on tags.

Useful links

• linux-cip-pipelines
• linux-cip

Acceptance criteria

• Tags pushed to linux-cip no longer trigger CI pipelines