Use builtin compile in doc example

Follow up to #7438

doc/en/example/assertion/failure_demo.py

@@ -1,4 +1,3 @@
-import _pytest._code
 import pytest
 from pytest import raises
 
@@ -197,7 +196,7 @@ def test_dynamic_compile_shows_nicely():
     name = "abc-123"
     spec = importlib.util.spec_from_loader(name, loader=None)
     module = importlib.util.module_from_spec(spec)
-    code = _pytest._code.compile(src, name, "exec")
+    code = compile(src, name, "exec")
     exec(code, module.__dict__)
     sys.modules[name] = module
     module.foo()