Update spell-checker ignore list in mode.rs

Author: sylvestre

src/uucore/src/lib/features/mode.rs

@@ -5,7 +5,7 @@
 
 //! Set of functions to parse modes
 
-// spell-checker:ignore (vars) fperm srwx
+// spell-checker:ignore (vars) fperm srwx RAII
 
 use libc::umask;