Remove no contributors found text when emails are disabled

Created by: philipp-spiess

Part of #31214 (closed) Fixes #32123 (closed)

If you take a look at this test plan it's rather odd that we show a message saying that we haven't found collaborators when the real reason is that email is not configured.

We could also add a hint here for site admins to enable emails. WDYT @rrhyne @slimsag?

Test plan

Here's a dotcom version with email disabled but invites enabled: