complete: remove stale comment

Commit a4b6348315 (clippy: fix collapsible_match lint, 2026-04-18) made
it so '$' characters are handled here, which contradicts the comment.
Remove it.

src/complete.rs

@@ -1752,9 +1752,7 @@ enum Mode {
                         mode = DoubleQuoted;
                     }
                 }
-                _ => {
-                    // all other chars ignored here
-                }
+                _ => (),
             }
         }