AES not enabled on AArch64

[betelgeuse]

README says the library should automatically enable AES on AArch64

aHash/README.md

Line 60 in 7d5c661

* `nightly-arm-aes`: To use AES instructions on 32-bit ARM, which requires nightly. This is not needed on AArch64.

However, in source code we can see that aarch64 is combined with the nightly-arm-aes feature being enabled

aHash/src/lib.rs

Line 111 in 7d5c661

all(feature = "nightly-arm-aes", target_arch = "aarch64", target_feature = "aes", not(miri)),

[briansmith]

PR #268 attempts to fix this.