test: increase coverage internal readline

PR-URL: #24150
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-readline-keys.js

@@ -99,11 +99,12 @@ addTest('\n\r\t', [
 ]);
 
 // space and backspace
-addTest('\b\x7f\x1b\b\x1b\x7f \x1b ', [
+addTest('\b\x7f\x1b\b\x1b\x7f\x1b\x1b  \x1b ', [
   { name: 'backspace', sequence: '\b' },
   { name: 'backspace', sequence: '\x7f' },
   { name: 'backspace', sequence: '\x1b\b', meta: true },
   { name: 'backspace', sequence: '\x1b\x7f', meta: true },
+  { name: 'space', sequence: '\x1b\x1b ', meta: true },
   { name: 'space', sequence: ' ' },
   { name: 'space', sequence: '\x1b ', meta: true },
 ]);