Remove the limit of number of commands per extension, but keep the limit of 4 shortcuts per extensi…

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

 <table class="intro">
   <tr>
     <th scope="col"></th>
     <th scope="col"></th>
   </tr>
   <tr>
     <td><strong>Description:</strong></td>
     <td>Use the commands API to add keyboard shortcuts
     that trigger actions in your extension,
     for example, an action to open the browser action
@@ skipping 15 matching lines @@
 </p>
 
 <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
 the manifest as an attribute of the 'commands' manifest key. Note: Combinations
 that involve Ctrl+Alt are not permitted in order to avoid conflicts with the
 AltGr key. Also note that on Mac 'Ctrl' is automatically converted to 'Command'.
 If you want 'Ctrl' instead, please specify 'MacCtrl'.</p>
 
+<p>An extension can have many commands but only 4 suggested keys can be
+specified. The user can manually add more shortcuts from the chrome://extensions
+page.</p>
+
 <pre>{
   "name": "My extension",
   ...
 <b>  "commands": {
     "toggle-feature-foo": {
       "suggested_key": {
         "default": "Ctrl+Shift+Y",
         "mac": "Command+Shift+Y"
       },
       "description": "Toggle feature foo"
@@ skipping 26 matching lines @@
   console.log('Command:', command);
 });
 </pre>
 
 <p>The '_execute_browser_action' and '_execute_page_action' commands are
 reserved for the action of opening your extension's popups. They won't normally
 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>