Try reproducing the MinGW hang on time command (#6168)

to see if it really exits correctly. 

GitHub Support asked me to confirm the command is exiting correctly.

.github/workflows/mingw.yml

@@ -135,7 +135,7 @@ jobs:
         run: |
           # Actions uses UTF8, causes test failures, similar to normal OS setup
           chcp.com 437
-          make ${{ StartsWith(matrix.test_task, 'test/') && matrix.test_task || 'test-all' }}
+          time make ${{ StartsWith(matrix.test_task, 'test/') && matrix.test_task || 'test-all' }}
         env:
           RUBY_TESTOPTS: >-
             -j${{env.TEST_JOBS}} --retry --job-status=normal --show-skip --timeout-scale=1.5

test/rinda/test_rinda.rb

@@ -496,10 +496,6 @@ class TupleSpaceProxyTest < Test::Unit::TestCase
   include TupleSpaceTestModule
 
   def setup
-    if RUBY_PLATFORM.match?(/mingw/)
-      @omitted = true
-      omit 'This test seems to randomly hang on GitHub Actions MinGW UCRT64'
-    end
     super
     ThreadGroup.new.add(Thread.current)
     @ts_base = Rinda::TupleSpace.new(1)
@@ -507,9 +503,6 @@ class TupleSpaceProxyTest < Test::Unit::TestCase
     @server = DRb.start_service("druby://localhost:0")
   end
   def teardown
-    return if @omitted
-    @omitted = false
-
     # implementation-dependent
     @ts_base.instance_eval{
       if th = @keeper