I had this warning show up in the iOS Authenticator app like last week or something and it guides you through changing your iOS settings to instead use Edge as a password manager. As Edge is my browser of choice on my Windows PC and I already had it installed on iOS, this was a very minor inconvenience for me.
It's worth mentioning that even though I almost exclusively use Safari as a web browser on my iOS device, when filling in passwords on websites it seamlessly allows you to use any iOS configured password manager including Edge.
It's definitely a little weird that you now require Edge to also be installed for essentially the same functionally and Microsoft might be doing it to try push people to install Edge.