Revert "test_gc.rb: Attempt to stabilize test_interrupt_in_finalizer"

This reverts commit c1c0b32.

This test is clearly not reliable:
https://github.com/ruby/ruby/actions/runs/17446920961/job/49543543423

I want to skip this unstable test on GitHub Actions to make sure this
test doesn't prevent PRs from getting merged. We can continue to monitor
the state of this test on RubyCI and ci.rvm.jp.

Author: k0kubun

test/ruby/test_gc.rb

@@ -742,12 +742,13 @@ def test_exception_in_finalizer
   end
 
   def test_interrupt_in_finalizer
+    omit 'randomly hangs on many platforms' if ENV.key?('GITHUB_ACTIONS')
     bug10595 = '[ruby-core:66825] [Bug #10595]'
     src = <<-'end;'
       Signal.trap(:INT, 'DEFAULT')
       pid = $$
       Thread.start do
-        1000.times {
+        10.times {
           sleep 0.1
           Process.kill("INT", pid) rescue break
         }