Don't attempt to redeclare nesting scope

[jez]

Sorbet already knows how to handle

module A::B::C
end

out of the box. It doesn't require the programmer to write

module A; end
module A::B; end
module A::B::C
end

like you would have to if you were running this code like normal Ruby.

And this is important, because if it's ever the case that somewhere else
A or B are actually defined as classes, Sorbet is completely fine
with that:

# OK

module A; end
class A::B; end
module A::B::C
end

But if Sorbet ever sees conflicting definitions, then it will complain:

# ERROR

module A; end
class A; end

So we don't gain anything by having these declared explicitly, and also
in some cases it causes problems.

[jez]

@mdehoog if you have a moment for this I'd appreciate it 🙏

[mdehoog]

nice cleanup!