Linker: Deprecate formatSize()

Linker: Deprecate formatSize()

This is a static function that uses global state through $wgLang, and
provides no benefit than calling Language::formatSize() directly aside
from escaping. But that should generally be handled closer to output
generation.

Change-Id: I35fdbaf2fcaa89f0d4442e1f63ec8ed29e0c339f