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

This reverts commit bee5089d67.

Looking at 7564065637,
we concluded that the ruby process for test-all is stuck before exit
when this issue reproduces.

However, because of our limited bandwidth to support MinGW, we're not
investigating this, and therefore we need to keep skipping tests that
hang on this environment.

.github/workflows/mingw.yml

@@ -135,7 +135,7 @@ jobs:
         run: |
           # Actions uses UTF8, causes test failures, similar to normal OS setup
           chcp.com 437
-          time make ${{ StartsWith(matrix.test_task, 'test/') && matrix.test_task || 'test-all' }}
+          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

@@ -496,6 +496,10 @@ 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)
@@ -503,6 +507,9 @@ 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