improve revoked key error message when composing

@tomholub now i get this error
<img width="461" alt="Screenshot 2022-04-22 at 17 06 11" src="https://user-images.githubusercontent.com/91205853/164730753-1c2c4628-7e9a-4cae-b7d9-8ee4dca4bb2a.png">

_Originally posted by @fcvakintos in https://github.com/FlowCrypt/flowcrypt-ios/issues/1491#issuecomment-1106552570_