Remove redundant return statement

This will make the Null Safety migration easier (the analyzer gets
smarter and would warn about non-reachable code).

PiperOrigin-RevId: 330904797
diff --git a/lib/support/stdio_stepper.dart b/lib/support/stdio_stepper.dart
index 6803daf..15b0c10 100644
--- a/lib/support/stdio_stepper.dart
+++ b/lib/support/stdio_stepper.dart
@@ -59,10 +59,7 @@
           return true;
         case 'quit':
         case 'q':
-          exit(-1);
-          // TODO(162213706): remove ignore below.
-          // ignore: dead_code
-          return false;
+          return exit(-1);
         default:
           print('invalid command: `$command` enter `h` or `help` for help.');
       }