Fix ruby 2.7 deprecation warning (#338)

* fix ruby 2.7 deprecation warning (Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call)

* update changelog

Co-authored-by: yrodnin <y.rodnin@balance-pl.ru>

Author: begotten63

CHANGELOG.md

@@ -6,7 +6,7 @@
 
 #### Fixes
 
-* Your contribution here.
+* [#338](https://github.com/ruby-grape/grape-entity/pull/338): Fix ruby 2.7 deprecation warning - [@begotten63](https://github.com/begotten63).
 
 ### 0.8.1 (2020-07-15)
 

lib/grape_entity/entity.rb

@@ -537,7 +537,7 @@ def delegate_attribute(attribute)
       if is_defined_in_entity?(attribute)
         send(attribute)
       elsif @delegator_accepts_opts
-        delegator.delegate(attribute, self.class.delegation_opts)
+        delegator.delegate(attribute, **self.class.delegation_opts)
       else
         delegator.delegate(attribute)
       end