docs: fix role typos in startSpeaking/stopSpeaking (#24550)

docs/api/menu.md

@@ -195,8 +195,8 @@ const template = [
         {
           label: 'Speech',
           submenu: [
-            { role: 'startspeaking' },
-            { role: 'stopspeaking' }
+            { role: 'startSpeaking' },
+            { role: 'stopSpeaking' }
           ]
         }
       ] : [