The test fails randomly for unknown reason.
3956294509
```
1) Error:
TestParallel::TestParallel#test_retry_workers:
Test::Unit::ProxyError: execution expired (start: 2025-03-28 04:04:10 +0000, end: 2025-03-28 04:05:50 +0000)
/home/runner/work/ruby/ruby/src/tool/test/testunit/test_parallel.rb:16:in 'TestParallel.timeout'
/home/runner/work/ruby/ruby/src/tool/test/testunit/test_parallel.rb:225:in 'TestParallel::TestParallel#test_retry_workers'
```
Maybe the workers do not respond "quit" request.
We no longer use the retry mechanism, so just remove the test.
When RUBY_TEST_TIMEOUT_SCALE is set, the timeout increases by the multiple
specified. However, the test in test4test_hungup.rb does not scale, so
if RUBY_TEST_TIMEOUT_SCALE is a large number like 10, then the test will
not time out causing the tests test to fail.
This test currently fails if RUBY_TEST_TIMEOUT_SCALE is set, because the
worker timeout is scaled out but the duration of the sleep does not;
thus, the test-test-case does not timeout when it should.
