Link to "User Settings" page from Gravatar settings page is broken

The link to the "User Settings" page from the Gravatar settings page doesn't work if your site is in a sub-directory. This is because the URL is hardcoded.

This patch fixes that by removing the leading "/" from /admin/user/settings, and running it through the url() function.

Steps to repeat problem.

1. Install drupal in a sub-directory of your domain
2. Install gravatar module
3. Navigate to admin/user/gravatar
4. Clicking on the link for "users settings page" at the top of the Gravatar settings page will take you to http://example.com/admin/user/settings when it should go to http://example.com/my-sub-directory/admin/user/settings

Applying this patch should fix that.