[ticket/12648] Improve tabs in ACP/UCP/MCP/Posting (fixes and cleanup)

https://tracker.phpbb.com/browse/PHPBB3-12648
https://tracker.phpbb.com/browse/PHPBB3-12443
https://tracker.phpbb.com/browse/PHPBB3-12605

PHPBB3-12648
Shouldn't the `<span>` be removed? Same for the options tab.