py/obj: Remove mp_generic_unary_op().

Since converting to variable sized slots in mp_obj_type_t, we can now
reduce the code size a bit by removing mp_generic_unary_op() and the
corresponding slots where it is used. Instead we just implement the
generic `__hash__` operation in the runtime.

Signed-off-by: David Lechner <david@pybricks.com>

py/obj.c

@@ -594,12 +594,3 @@ void mp_get_buffer_raise(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flag
         mp_raise_TypeError(MP_ERROR_TEXT("object with buffer protocol required"));
     }
 }
-
-mp_obj_t mp_generic_unary_op(mp_unary_op_t op, mp_obj_t o_in) {
-    switch (op) {
-        case MP_UNARY_OP_HASH:
-            return MP_OBJ_NEW_SMALL_INT((mp_uint_t)o_in);
-        default:
-            return MP_OBJ_NULL;      // op not supported
-    }
-}