Fix Chrome OS spelling in documentation

chrome/common/extensions/docs/templates/intros/commands.html

 <h2 id="manifest">Manifest</h2>
 <p>
 You must have a <code>"manifest_version"</code> of at least <code>2</code> to use this API.
 </p>
 
 {{?is_apps +partials.warning_dev /}}
 
 <h2 id="usage">Usage</h2>
 <p>The commands API allows you to define specific commands, and bind them to a
 default key combination. Each command your extension accepts must be listed in
@@ skipping 67 matching lines @@
 generate events that you can handle. If you need to take action based on your
 popup opening, consider listening for an 'onDomReady' event inside your popup's
 code.
 </p>
 
 <h2 id="usage">Scope</h2>
 <p>By default, Commands are scoped to the Chrome browser, which means that while
 the browser does not have focus, the shortcut will be inactive. On desktop
 Chrome, Commands can instead have global scope, as of version 35, and will then
 also work while Chrome does *not* have focus. NOTE: The exception here is
-ChromeOS, where global commands are not allowed at the moment.</p>
+Chrome OS, where global commands are not allowed at the moment.</p>
 
 <p>The user is free to designate any shortcut as global using the UI in
 chrome://extensions \ Keyboard Shortcuts, but the extension developer is limited
 to specifying only Ctrl+Shift+[0..9] as global shortcuts. This is to minimize
 the risk of overriding shortcuts in other applications since if, for example,
 Alt+P were to be allowed as global, the printing shortcut might not work in
 other applications.</p>
 
 <p>Example:</p>
 
 <pre data-filename="manifest.json">
 {
   "name": "My extension",
   ...
   "commands": {
     "toggle-feature-foo": {
       "suggested_key": {
         "default": "Ctrl+Shift+5"
       },
       "description": "Toggle feature foo",
       <b>"global": true</b>
     }
   },
   ...
 }</pre>