Fix Rubocop warnings

Author: andrykonchin

core/proc/parameters_spec.rb

@@ -64,7 +64,7 @@
   end
 
   it "regards keyword parameters in lambdas as required" do
-    lambda {|x:| }.parameters.first.first.should == :keyreq
+    -> x: { }.parameters.first.first.should == :keyreq
   end
 
   it "sets the first element of each sub-Array to :rest for parameters prefixed with asterisks" do

language/block_spec.rb

@@ -737,8 +737,8 @@ def obj.to_ary; raise "Exception raised in #to_ary" end
     end
 
     it "accepts unnamed arguments" do
-      lambda { |_,_| }.should be_an_instance_of(Proc)
-      ->(_,_) {}.should be_an_instance_of(Proc)
+      lambda { |_,_| }.should be_an_instance_of(Proc) # rubocop:disable Style/Lambda
+      -> _,_ {}.should be_an_instance_of(Proc)
       Proc.new { |_,_| }.should be_an_instance_of(Proc)
     end
   end