Fix TypeScript doc comment (#23)

Author: dario-piotrowicz

index.d.ts

@@ -1,7 +1,7 @@
 /**
 Convert Windows backslash paths to slash paths: `foo\\bar` ➔ `foo/bar`.
 
-[Forward-slash paths can be used in Windows](http://superuser.com/a/176395/6877) as long as they're not extended-length paths and don't contain any non-ascii characters.
+[Forward-slash paths can be used in Windows](http://superuser.com/a/176395/6877) as long as they're not extended-length paths.
 
 @param path - A Windows backslash path.
 @returns A path with forward slashes.