Remove reference to env var
Remove reference to env var

The check was moved to compile time and was not intended to be user-facing
aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,SingingTree/rustfmt,graydon/rust,aidancully/rust,SingingTree/rustfmt,rust-lang/rustfmt,graydon/rust,rust-lang/rustfmt