Skip fault handler test on 3.15

Summary: This test is unhappy that we have an extension module installed.

Reviewed By: yoney

Differential Revision: D92742843

fbshipit-source-id: 3cf11702c755d54f1e6bfd7957d06a5b5542e95d

Author: DinoV

cinderx/TestScripts/cinder_skip_test_315.txt

@@ -4,3 +4,6 @@ test.test_traceback.MiscTest.test_windows_only_module_error
 
 # T249123927
 test.test_generators.GeneratorTest.test_close_clears_frame
+
+# cinderx extension module is installed so output differs
+test.test_faulthandler.FaultHandlerTests.test_dump_ext_modules