Remove multivariate test for menu topic text

This reverts commits d23e6695737ed2ce6b5c8d6ef20496911a251fb7
ba4dc8e0c89be9545a04cbd3f9f8a9ded241bb46 and
95b3eeb834f436f35dadf61386a4c35a93c64a93.
Merge pull request #1227 from alphagov/disable-topics-text-multivariate-test

Remove multivariate test for menu topic text