Add details to contact org admin for repos outside of the dotnet org

[riarenas]

Adding a short remark about repos that aren't part of the dotnet org.

related to #2134

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/core-eng/tree/master/Documentation/Validation

[dagood]

Thanks! Maybe this line should be outside the bulleted list of "not hard requirements" (after?) but either way, I would have seen this line and knew it applied to my situation. 😄

[riarenas]

Ha! I didn't notice that remark. I'll put it before that.

[MattGal]

I think we may just be waiting for someone to approve the request, but LGTM.