fix: Update xray_cause_test for Ruby 3.4+ backtrace format

Ruby 3.4+ changed backtrace label from 'method_name' to
'ClassName#method_name'. Use assert_includes to handle both formats.

Author: anzheyazzz

test/unit/xray_cause_test.rb

@@ -25,7 +25,7 @@ def test_xray_cause
     assert_true under_test.instance_variable_get(:@cause)[:exceptions][0][:stack].count.positive?
     assert_equal __FILE__, under_test.instance_variable_get(:@cause)[:exceptions][0][:stack][0][:path]
     assert_kind_of Integer, under_test.instance_variable_get(:@cause)[:exceptions][0][:stack][0][:line]
-    assert_equal __method__.to_s, under_test.instance_variable_get(:@cause)[:exceptions][0][:stack][0][:label]
+    assert_includes under_test.instance_variable_get(:@cause)[:exceptions][0][:stack][0][:label], __method__.to_s
   end
 
   def test_stack_depth_maximum