Use project_with_code factory where necessary

app/views/admin/projects/show.html.haml

features/steps/project/project_browse_commits.rb

spec/controllers/commit_controller_spec.rb

spec/controllers/commits_controller_spec.rb

spec/controllers/merge_requests_controller_spec.rb

spec/controllers/tree_controller_spec.rb

spec/features/gitlab_flavored_markdown_spec.rb

spec/helpers/gitlab_markdown_helper_spec.rb