Fixes validator warnings in runner jest tests

What does this MR do and why?

Two of our jest runner suites have several warnings attached to them, due to a faulty mounting of the GlTable.

This change fixes the issue by stubbing the table component out when needed.

Screenshots or screen recordings

Before	After

How to set up and validate locally

We will generate the runner fixtures in case they are out of date, and then run the specs:

$ bundle exec rspec -f d {ee/spec,spec}/frontend/fixtures/runner.rb spec/frontend/fixtures/runner_instructions.rb
$ yarn jest spec/frontend/ci/runner/components/runner_list_spec.js ee/spec/frontend/ci/runner/components/runner_active_list_spec.js

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #425764 (closed)