docs: remove COPYING.html from website/www tree.

The file should not be published. It gets published as license.html
and linked as such from the side menu.

Author: rouilj

website/www/conf.py

@@ -89,6 +89,7 @@
                     'docs/whatsnew-0.8.txt',
                     'robots.txt',
                     'docs/tracker_config.txt',
+                    'COPYING.txt',
                     '_tmp']
 
 # The reST default role (used for this markup: `text`) to use for all documents.