Fix Ruby 2.7 keyword deprecation warning in validators/coerce (#2131)

Author: K0H205

CHANGELOG.md

@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#2131](https://github.com/ruby-grape/grape/pull/2131): Fix Ruby 2.7 keyword deprecation warning in validators/coerce - [@K0H205](https://github.com/K0H205).
 
 ### 1.5.1 (2020/11/15)
 

lib/grape/validations/validators/coerce.rb

@@ -17,7 +17,7 @@ class Instance
 
   module Validations
     class CoerceValidator < Base
-      def initialize(*_args)
+      def initialize(attrs, options, required, scope, **opts)
         super
 
         @converter = if type.is_a?(Grape::Validations::Types::VariantCollectionCoercer)