Sync Py_TPFLAGS_MANAGED_DICT for PyPy3.11 across the codebase

Adjust the `Py_TPFLAGS_MANAGED_DICT` logic in `include/pybind11/attr.h`
to match the one used in `include/pybind11/detail/class.h`.

This is a followup to pybind#5508.

Author: mgorny

include/pybind11/attr.h

@@ -359,7 +359,8 @@ struct type_record {
 
         bases.append((PyObject *) base_info->type);
 
-#if PY_VERSION_HEX < 0x030B0000
+// Keep in sync with enable_dynamic_attributes() in detail/class.h
+#if PY_VERSION_HEX < 0x030B0000 || defined(PYPY_VERSION)
         dynamic_attr |= base_info->type->tp_dictoffset != 0;
 #else
         dynamic_attr |= (base_info->type->tp_flags & Py_TPFLAGS_MANAGED_DICT) != 0;