Fix wrong description of chrome.commands example.

chrome/common/extensions/docs/examples/api/commands/manifest.json

 {
   "name": "Sample Extension Commands extension",
-  "description": "Press Ctrl+F to open the browser action popup, press Ctrl+Shift+Y to send an event (Command+Shift+Y on a Mac).",
+  "description": "Press Ctrl+Shift+F (Command+Shift+F on a Mac) to open the browser action popup, press Ctrl+Shift+Y to send an event (Command+Shift+Y on a Mac).",
   "version": "1.0",
   "manifest_version": 2,
   "background": {
     "scripts": ["background.js"],
     "persistent": false
   },
   "browser_action": {
     "default_popup": "browser_action.html"
   },
   "commands": {
     "toggle-feature": {
       "suggested_key": { "default": "Ctrl+Shift+Y" },
       "description": "Send a 'toggle-feature' event to the extension"
     },
     "_execute_browser_action": {
       "suggested_key": {
         "default": "Ctrl+Shift+F",

[zhchbin, 2013/09/01 02:44:12]

The browser action of this example is using "Ctrl+Shift+F", but the description
is saying: "Ctrl+F".

         "mac": "MacCtrl+Shift+F"
       }
     }
   }
 }