Back out #850 (#1079)

Fixes #1042 (and probably #1044 which looks like the same thing).

The issue with the "obviously unnecessary" parentheses that #850 removed is that sometimes they're necessary to help Black fit something in one line. I didn't see an obvious solution that still removes the parens #850 was intended to remove, so let's back out this change for now in the interest of unblocking a release.

This PR also adds a test adapted from the failing example in #1042, so that if we try to reapply the #850 change we don't break the same case again.