[Remove] lang reference

[kjaymiller]

Multiple languages were removed... this should be removed.

The condition comparing 'lang' to itself is always true; consider comparing the loop variable to the current page language (e.g. {% if page.lang == lang %}).

Originally posted by @Copilot in https://github.com/BlackPythonDevs/blackpythondevs.github.io/pull/717#discussion_r2169998101