Revert r64471

* This reverts commit 9ab04897bd:
  "don't run specs add at r64409 on Windows"
* It doesn't seem to help:
  http://mswinci.japaneast.cloudapp.azure.com/vc12-x64/ruby-trunk/recent.html

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/library/conditionvariable/wait_spec.rb

@@ -23,7 +23,6 @@ describe "ConditionVariable#wait" do
     th.join
   end
 
-  platform_is_not :windows do
   it "reacquires the lock even if the thread is killed" do
     m = Mutex.new
     cv = ConditionVariable.new
@@ -120,4 +119,3 @@ describe "ConditionVariable#wait" do
     threads.each(&:join)
   end
 end
-end