Remove unnecessary `select` method for `CollectionProxy`

Currently `CollectionProxy` inherits `Relation` and `Relation` includes
`QueryMethods`. This method is completely duplicated.

https://github.com/rails/rails/blob/v5.0.0/activerecord/lib/active_record/relation/query_methods.rb#L271-L275

activerecord/lib/active_record/associations/collection_association.rb

@@ -82,14 +82,6 @@ def reset
         @target = []
       end
 
-      def select(*fields)
-        if block_given?
-          load_target.select.each { |e| yield e }
-        else
-          scope.select(*fields)
-        end
-      end
-
       def find(*args)
         if block_given?
           load_target.find(*args) { |*block_args| yield(*block_args) }

activerecord/lib/active_record/associations/collection_proxy.rb

@@ -53,6 +53,12 @@ def loaded?
         @association.loaded?
       end
 
+      ##
+      # :method: select
+      #
+      # :call-seq:
+      #   select(*fields, &block)
+      #
       # Works in two ways.
       #
       # *First:* Specify a subset of fields to be selected from the result set.
@@ -106,9 +112,6 @@ def loaded?
       #   #      #<Pet id: 2, name: "Spook">,
       #   #      #<Pet id: 3, name: "Choo-Choo">
       #   #    ]
-      def select(*fields, &block)
-        @association.select(*fields, &block)
-      end
 
       # Finds an object in the collection responding to the +id+. Uses the same
       # rules as ActiveRecord::Base.find. Returns ActiveRecord::RecordNotFound