Bump MSRV to 1.89

[dishmaker]

After cargo update

aes v0.9.3 release:

• Release aes v0.9.3 block-ciphers#587

  error: rustc 1.85.0 is not supported by the following package:
    aes@0.9.3 requires rustc 1.89

[cschramm]

Nothing enforces aes 0.9.3 and thus this MSRV. cargo update should be fine with the version-aware solver

[dishmaker]

Oh, sorry. That's just needed for tests:

• refactor: use *Ref (or *Owned) der types from RustCrypto/formats #706