Update outdated comment
Update outdated comment

The highest-priority item is the *first* in the list, not the last.
See [this code][1] for more.

[this code]: https://github.com/rust-lang/rust/blob/0e63af5da3400ace48a0345117980473fd21ad73/compiler/rustc_mir_build/src/build/matches/mod.rs#L1334-L1335

aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust