Improve QA specs for merge request rebasing and squashing

The following discussions from !4288 (merged) should be addressed:

• @grzesiek commented on a discussion: (+6 comments)

  On this line, project is a fist-class local variable, so we can use it instead of going thorough merge request, right?

• @felipe_artur started a discussion: (+1 comment)

  @grzesiek This might be the error cause. Instead of defining the method as a value it was passing a block. So everytime the factory was invoking the product the result was different. For example:

          product :name do
            Page::Project::Show.act { project_name }
          end

  It was being invoked while not on a project page, which was causing the spec to fail.

  Lets see if it passes now.

• @grzesiek started a discussion:

  I wonder if we should add project.repository_location using a factory product? It seems to be a frequent use case.