Update references to the GitHub repository

Author: eregon

README.md

@@ -26,7 +26,7 @@ ruby/spec is known to be tested in these implementations for every commit:
 
 * [MRI](https://rubyci.org/) on 30 platforms and 4 versions
 * [JRuby](https://github.com/jruby/jruby/tree/master/spec/ruby) for both 1.7 and 9.x
-* [TruffleRuby](https://github.com/oracle/truffleruby/tree/master/spec/ruby)
+* [TruffleRuby](https://github.com/truffleruby/truffleruby/tree/master/spec/ruby)
 * [Opal](https://github.com/opal/opal/tree/master/spec)
 * [Artichoke](https://github.com/artichoke/spec/tree/artichoke-vendor)
 

core/array/shared/unshift.rb

@@ -49,7 +49,7 @@
     -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(FrozenError)
   end
 
-  # https://github.com/oracle/truffleruby/issues/2772
+  # https://github.com/truffleruby/truffleruby/issues/2772
   it "doesn't rely on Array#[]= so it can be overridden" do
     subclass = Class.new(Array) do
       def []=(*)