Improve spec description

Author: eregon

spec/ruby/core/hash/ruby2_keywords_hash_spec.rb

@@ -7,7 +7,7 @@
       Hash.ruby2_keywords_hash?({}).should == false
     end
 
-    it "returns true if the Hash is a keywords Hash" do
+    it "returns true if the Hash is a keywords Hash marked by Module#ruby2_keywords" do
       obj = Class.new {
         ruby2_keywords def m(*args)
           args.last

spec/tags/core/hash/ruby2_keywords_hash_tags.txt

@@ -1 +1 @@
-fails:Hash.ruby2_keywords_hash? returns true if the Hash is a keywords Hash
+fails:Hash.ruby2_keywords_hash? returns true if the Hash is a keywords Hash marked by Module#ruby2_keywords