wallet2 `frozen` incorrectly asserts key image ordering and causes error on multisig tx signing
A [recent commit](https://github.com/monero-project/monero/commit/dc24312bc3c8c9d865e4576631832c81d6dd212d) to wallet2's `frozen` function incorrectly [asserts that key images are ordered](https://github.com/monero-project/monero/blob/ab826008d614a3722398642942c291be9650be6d/src/wallet/wallet2.cpp#L2008), resulting in the error `Mismatched key image b/t vin and construction data` when multisig participants sync key images such that they're ordered differently.

This issue requests fixing the assertion to not rely on key image ordering.