Skip running a DRb test on MinGW

It hangs even after a retry
https://github.com/ruby/ruby/runs/7966439530?check_suite_focus=true

We contacted GitHub Suppport about this before, and we concluded that
the problem is on our end. Unfortunately we don't have a bandwidth to
fix this MinGW problem, so until we get to work on it, this should be
just skipped to avoid a sporadic CI timeout.

test/drb/drbtest.rb

@@ -90,6 +90,7 @@ module DRbBase
   end
 
   def teardown
+    return if @omitted
     @ext.stop_service if defined?(@ext) && @ext
     if defined?(@service_name) && @service_name
       @drb_service.manager.unregist(@service_name)

test/drb/test_drbssl.rb

@@ -41,6 +41,10 @@ end
 class TestDRbSSLCore < Test::Unit::TestCase
   include DRbCore
   def setup
+    if RUBY_PLATFORM.match?(/mingw/)
+      @omitted = true
+      omit 'This test seems to randomly hang on GitHub Actions MinGW'
+    end
     @drb_service = DRbSSLService.new
     super
     setup_service 'ut_drb_drbssl.rb'

test/rinda/test_rinda.rb

@@ -498,7 +498,7 @@ class TupleSpaceProxyTest < Test::Unit::TestCase
   def setup
     if RUBY_PLATFORM.match?(/mingw/)
       @omitted = true
-      omit 'This test seems to randomly hang on GitHub Actions MinGW UCRT64'
+      omit 'This test seems to randomly hang on GitHub Actions MinGW'
     end
     super
     ThreadGroup.new.add(Thread.current)