Standardize on locale file not saying `%n$s` unless necessary
Summary:
The goal of this is https://phabricator.wikimedia.org/T413532 - making the upstream locale file match with itself modified by translatewiki's scripts. This helps catch a lot of errors, and it's neater too.
Also fix an outright erroneous case where the wrong string was being substituted.
Test Plan: Read the locale file.
Reviewers: O1 Blessed Committers, aklapper
Reviewed By: O1 Blessed Committers, aklapper
Subscribers: aklapper, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26623