check-shims should ignore typed: ignore files

[Morriar]

Consider this:

# file: sorbet/rbi/annotations/foo.rbi
# typed: true

class Foo; end

# file: sorbet/rbi/gems/[email protected]
# typed: ignore

class Foo; end

The check-shims command will complain that the definition for Foo is duplicated between the generated gem RBI and the annotations. Yet the generated gem RBI was generated with typed-override: ignore meaning that the RBI file for the gem is written on disk with typed: ignore thus not even seen by Sorbet. In this case the duplication is justified.

We should ignore files marked typed: ignore when running check-shims.

[Morriar]

Not this could also happen between a shim and a generate gem RBI file.