TestRegexp#test_match_cache_positive_look_behind: Extend the timeout limit

Author: mame

test/ruby/test_regexp.rb

@@ -1929,7 +1929,7 @@ def test_match_cache_atomic_complex
   end
 
   def test_match_cache_positive_look_ahead
-    assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}")
+    assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}", timeout: 30)
       timeout = #{ EnvUtil.apply_timeout_scale(10).inspect }
     begin;
        Regexp.timeout = timeout