Unset params as well as declared params

Without this change, I get parameters duplicated in my routes. Here's an example:

    module API
      module V1
        class Foo < Grape::API      
          desc 'foo'
          resource :foo do
            
            desc 'list foo' do
              entity FooEntity
              failure [
                [403, "Unauthorized"]
              ]
            end
            params do
              optional :lol, desc: "Type of foo to return", type: String, values: %w{a b c d}
            end
            get do
              @foo = current_account.foo
              
              present @foo, with: FooEntity
            end
            
            desc 'create new Foo'
            params do
              requires :foo, desc: "bar"
            end
            post do
              @foo = [create_foo!(params[:foo])]
              
              present @foo, with: FooEntity
            end
          end
        end
      end
    end

produces:

    {
      "apiVersion":"v1",
      "apis":[
        {
          "operations":[
            {
              "method":"GET",
              "nickname":"GET--version-foos---format-",
              "notes":"",
              "parameters":[
                {
                  "allowMultiple":false,
                  "description":"Type of foos to return",
                  "enum":[
                    "a",
                    "b",
                    "c",
                    "d"
                  ],
                  "name":"filter",
                  "paramType":"query",
                  "required":false,
                  "type":"string"
                }
              ],
              "responseMessages":[
                {
                  "code":403,
                  "message":"Unauthorized"
                }
              ],
              "summary":"list foos",
              "type":"API::V1::FooEntity"
            },
            {
              "method":"POST",
              "nickname":"POST--version-foos---format-",
              "notes":"",
              "parameters":[
                {
                  "allowMultiple":false,
                  "description":"Type of foos to return",
                  "enum":[
                    "a",
                    "b",
                    "c",
                    "d"
                  ],
                  "name":"filter",
                  "paramType":"form",
                  "required":false,
                  "type":"string"
                },
                {
                  "allowMultiple":false,
                  "description":"bar",
                  "name":"lol",
                  "paramType":"form",
                  "required":true,
                  "type":"string"
                }
              ],
              "summary":"create new foo",
              "type":"void"
            }
          ],
          "path":"/v1/foos.{format}"
        }
      ],
      "basePath":"http://localhost:3000/newapi",
      "models":{},
      "produces":[
        "application/json"
      ],
      "resourcePath":"/foos",
      "swaggerVersion":"1.2"
    }

(This is a redacted version of my real code)

Notice that the filter parameter is present on the get and the post routes, when it should be on just the get route. The patch fixes this problem, bringing the behaviour in line with grape 0.90.

If I have misunderstood something, my apologies.