py: Wrap .__class__ handling in MICROPY_CPYTHON_COMPAT.

Because it's superfluos in the presence of type(), a remenant from Python's
"old classes".
diff --git a/py/runtime.c b/py/runtime.c
index daa555e..f7a5554 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -716,10 +716,13 @@
 
     // if nothing found yet, look for built-in and generic names
     if (dest[0] == MP_OBJ_NULL) {
+#if MICROPY_CPYTHON_COMPAT
         if (attr == MP_QSTR___class__) {
             // a.__class__ is equivalent to type(a)
             dest[0] = type;
-        } else if (attr == MP_QSTR___next__ && type->iternext != NULL) {
+        } else
+#endif
+        if (attr == MP_QSTR___next__ && type->iternext != NULL) {
             dest[0] = (mp_obj_t)&mp_builtin_next_obj;
             dest[1] = base;
         } else if (type->load_attr == NULL) {