Fix flakey groups analytics menu test

What does this MR do and why?

Test introduced in !138976 (merged) should have been using group.full_path

How to set up and validate locally

bin/rspec ee/spec/lib/sidebars/groups/menus/analytics_menu_spec.rb

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 #433420 (closed)