Motivation

The changes in #5525 raced with a change in Stripe's codebase that caused it to
introduce problems. Blocks can take block arguments, and we don't do a great job
of modeling that right now. It used to be fine because we would just ignore the
error when passing blocks to a .call function on a proc type, because the
procs.rbi file was not # typed: strict

Eventually we might want to make it possible to declare proc types that take
blocks (and for that matter: keyword args) but I'm punting on that for today.

Test plan

See included automated tests.