make api doc name param recognizable by declared

[calfzhou]

I use a after_validation to my api to make sure that all endpoints only get declared params, code sample like:

after_validation do
  @raw_params = params
  @params = declared(params, include_missing: false)
end

But this will make swagger doc not available, because this after_validation also applies to swagger doc related endpoints, but the required param :name cannot be recognized by declared.

So i made this PR to make swagger doc endpoints' :name param being declared.

[dblock]

Yes, this is much better and now actually possible. The old syntax is from a very old version of Grape.

[dblock]

I merged a bit too quickly, I think a CHANGELOG line is actually useful here, if you can please PR one?