doc: fix description tags on web page.

Author: rouilj

website/www/index.txt

@@ -6,14 +6,14 @@ Roundup Issue Tracker
    :title: Roundup Issue Tracker
    :description: A simple-to-use and -install issue-tracking system
        with command-line, web, REST, XML-RPC and e-mail interfaces.
-       Adaptable to many uses cases. Allows you to customise the look
+       Adaptable to many use cases. Allows you to customize the look
        and feel and implement different workflows.
    :og\:type: website
    :og\:url: https://www.roundup-tracker.org/
    :og\:title: Roundup Issue Tracker
    :og\:description: A simple-to-use and -install issue-tracking system
        with command-line, web, REST, XML-RPC and e-mail interfaces.
-       Adaptable to many uses cases. Allows you to customise the look
+       Adaptable to many use cases. Allows you to customize the look
        and feel and implement different workflows.
    :og\:image: https://www.roundup-tracker.org/_images/index_logged_out.png