Follows-up on:

• T167238: Fatal Error: "Tag hook for noexternallanglinks is not callable" (1.30.0-wmf.4/includes/parser/Parser.php)
• https://gerrit.wikimedia.org/r/357523 (which fixed breakage from https://gerrit.wikimedia.org/r/356174

I believe this is the third or fourth time a fatal error from Wikibase parser hooks made its way to production. Localisation update, magic word corruption, and others. This time it was just broken code that never worked. Ideally, QA processes would have caught this post-merge, but perhaps it's uncommon or hard to test in beta.

Either way, it seems this code is overdue to have a basic integration test or unit test so that it executes at least once.