Usher bug on JN.1.16.1+S:L456V/JN.1.18+S:R346K

[xz-keg]

JN.1.16 is JN.1+S:F456L(T22928C)+S:R346T, and there is an S:L456V(C22928G) branch under it.

Given it is a single-nuc mutation on 22928, it is very unlikely for this position to mutate so frequently, a better explanation shall be JN.1.18(JN.1+S:R346T)+S:F456V(T22928G).

Seems that this is something related to the fundamental algorithm of usher, we previously see this bug in HK.1.1(retracted) too, where usher categorizes EG.5.1.1+S:G257D+S:L455F seqs as EG.5.1.1+S:G257V+S:L455F+S:V257D.

@AngieHinrichs