Fix watch mode docs (utf 8 now) (jestjs#6297)

Author: rickhanlonii

docs/WatchPlugins.md

@@ -116,7 +116,7 @@ key and the prompt:
 class MyWatchPlugin {
   getUsageInfo(globalConfig) {
     return {
-      key: 's'.codePointAt(0),
+      key: 's',
       prompt: 'do something',
     };
   }