printf: use is_ascii_control() for shell quoting

Replace manual ASCII control char check with is_ascii_control() to
properly handle both chars 0-31 and DEL (0x7F).

Author: sylvestre

src/uucore/src/lib/features/quoting_style/shell_quoter.rs

@@ -191,11 +191,8 @@ fn initial_quoting(
     always_quote: bool,
     check_control_chars: bool,
 ) -> (Quotes, bool) {
-    const ASCII_CONTROL_LIMIT: u8 = 32;
-
     let has_special_chars = input.iter().any(|c| {
-        shell_escaped_char_set(dirname).contains(c)
-            || (check_control_chars && *c < ASCII_CONTROL_LIMIT)
+        shell_escaped_char_set(dirname).contains(c) || (check_control_chars && c.is_ascii_control())
     });
 
     if has_special_chars {
@@ -255,7 +252,7 @@ mod tests {
 
     #[test]
     fn test_initial_quoting() {
-        // Control chars (< 32) force single quotes in escape mode
+        // Control chars (0-31 and 0x7F) force single quotes in escape mode
         assert_eq!(
             initial_quoting(b"\x01", false, false, true),
             (Quotes::Single, true)