increase timeout for high load env

I can reproduce timeout failure with the high load machine:

```
$ RUBY_MAX_CPU=100 ruby -e '100.times{Ractor.new{loop{}}}; sleep' &
$ while make test-all -o exts -o encs TESTS='ruby/gc -n /test_interrupt_in_finalizer/ --repeat-count=100'; do date; done
....
Finished(93/100)  tests in 0.653434s, 1.5304 tests/s, 7.6519 assertions/s.
Finished(94/100)  tests in 0.614422s, 1.6275 tests/s, 8.1377 assertions/s.
[1/1] TestGc#test_interrupt_in_finalizer = 11.08 s
  1) Timeout:
TestGc#test_interrupt_in_finalizer
```

Author: ko1

test/ruby/test_gc.rb

@@ -757,7 +757,7 @@ def test_interrupt_in_finalizer
         ObjectSpace.define_finalizer(Object.new, f)
       end
     end;
-    out, err, status = assert_in_out_err(["-e", src], "", [], [], bug10595, signal: :SEGV) do |*result|
+    out, err, status = assert_in_out_err(["-e", src], "", [], [], bug10595, signal: :SEGV, timeout: 100) do |*result|
       break result
     end
     unless /mswin|mingw/ =~ RUBY_PLATFORM