Fix UI tests (#12642)

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg_max_encoded_len.stderr

@@ -14,4 +14,4 @@ error[E0277]: the trait bound `Vec<u8>: MaxEncodedLen` is not satisfied
              (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4, TupleElement5, TupleElement6)
              (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4, TupleElement5, TupleElement6, TupleElement7)
            and 78 others
-   = note: required because of the requirements on the impl of `StorageInfoTrait` for `frame_support::pallet_prelude::StorageValue<_GeneratedPrefixForStorageMyStorage<T>, Vec<u8>>`
+   = note: required for `frame_support::pallet_prelude::StorageValue<_GeneratedPrefixForStorageMyStorage<T>, Vec<u8>>` to implement `StorageInfoTrait`