Revert "Add test to ensure that concurrent message loops have at least one workers. (flutter#16074)"

This reverts commit f7f5319.

Author: NoamDev

fml/message_loop_unittests.cc

@@ -284,12 +284,6 @@ TEST(MessageLoop, TaskObserverFire) {
   ASSERT_TRUE(terminated);
 }
 
-TEST(MessageLoop, ConcurrentMessageLoopHasNonZeroWorkers) {
-  auto loop = fml::ConcurrentMessageLoop::Create(
-      0u /* explicitly specify zero workers */);
-  ASSERT_GT(loop->GetWorkerCount(), 0u);
-}
-
 TEST(MessageLoop, CanCreateAndShutdownConcurrentMessageLoopsOverAndOver) {
   for (size_t i = 0; i < 10; ++i) {
     auto loop = fml::ConcurrentMessageLoop::Create(i + 1);