`spec/features/explore/new_menu_spec.rb` is over-testing

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/features/explore/new_menu_spec.rb

This is a feature spec to ensure the "New" menu at the top works. It can easily be a view spec that verifies the href attribute of links is correct. It currently takes about 2 minutes.

@godfat @rymai Is this something that QA already implicitly exercises as a part of other tests, and maybe we can just delete this outright?