GC.stat key name

* test/-ext-/tracepoint/test_tracepoint.rb: follow the change of
  key name of GC.stat.

* test/ruby/test_hash.rb (TestHash#test_AREF_fstring_key): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47475 b2dd03c8-39d4-4d8f-98ff-823fe69b080e