Expose DangerfileGitLabPlugin#mr_changes

[rymai]

I wrongly assumed it was exposed already here: https://gitlab.com/gitlab-org/gitlab-dangerfiles/-/blob/8802a22a5e18cc13abe5e2ee39377a1eb0f1597f/lib/danger/plugins/helper.rb#L419 but it's not.

[orta]

The failure on AppVeyor does look legit:

  1) Danger::DangerfileGitLabPlugin#mr_changes sets the mr_changes
2426     Failure/Error: expect(plugin.mr_changes).to all(be_an_instance_of(Gitlab::ObjectifiedHash))
2427

[rymai]

The failure on AppVeyor does look legit:

  1) Danger::DangerfileGitLabPlugin#mr_changes sets the mr_changes
2426     Failure/Error: expect(plugin.mr_changes).to all(be_an_instance_of(Gitlab::ObjectifiedHash))
2427

Hmm, this passes locally. 🤔 Do you know how can I reproduce locally?

[rymai]

@orta Ok, I removed the first assertion as this wasn't really needed anyway.

[orta]

Cool beans, will try make a release now

[orta]

Shipped in 8.3.1