add a space

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44499 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test/ruby/test_gc.rb: use GC.stat(:key) instead of GC.stat

* test/ruby/test_gc.rb (TestGc#test_latest_gc_info): use
  GC.stat(:key) instead of GC.stat.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44500 b2dd03c8-39d4-4d8f-98ff-823fe69b080e