[rubygems/rubygems] Use File#open instead of Kernel#open

rubygems/rubygems@bfb3f67494

lib/rubygems/stub_specification.rb

@@ -113,8 +113,7 @@ def data
       begin
         saved_lineno = $.
 
-        # TODO It should be use `File.open`, but bundler-1.16.1 example expects Kernel#open.
-        open loaded_from, OPEN_MODE do |file|
+        File.open loaded_from, OPEN_MODE do |file|
           begin
             file.readline # discard encoding line
             stubline = file.readline.chomp