Remove the `From<InternedString> for String` impl.
Remove the `From<InternedString> for String` impl.

It's not used.

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