Follow-up from "Fix alignment of resend button in members page"

We're still introducing technical debt with duplicate code, but I understand us preferring this kind of debt over CSS. Since we're actually just refinancing our gitlab-ce~3011693, I'd feel more comfortable if we had a plan for paying it off... Could we:

• Create / find a follow up issue to resolve the duplication in _groups.html.haml + _member.html.haml.
• Add a comment in the two files referring to eachother's coupling with a link to the issue.

I can easily see a consistency regression being added by a community contributor / maintainer that's not familiar with this context (because it's not obvious).