fix outdated help text
fix outdated help text

rust-lang/rustfmt,flutterhash/rustfmt,SingingTree/rustfmt,aidancully/rust,Emilgardis/rustfmt,aidancully/rust,graydon/rust,Emilgardis/rustfmt,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,rust-lang/rustfmt,SingingTree/rustfmt,aidancully/rust,studoot/rustfmt,aidancully/rust,studoot/rustfmt