Restore MediaWiki:Maps after a failing config-save test and test the namespace check

[JeroenDeDauw]

Follows-up to #949

ConfigPageHooksTest saves MediaWiki:Maps on the wiki's real database, so a failing run left the invalid test
config as the wiki's live configuration. A save that goes through is now undone before the assertions run.

The test for other JSON pages changed namespace and title at once, so dropping the namespace half of the config-page
check went unnoticed. It now uses a page named Maps in the GeoJson namespace.

MapPrinter imports MapsFactory, and its tracking-category comment no longer claims for every caller what only
holds for #ask and #show.

_{AI-authored — Claude Code, Opus 5.5 (max); findings from a /review session of #949, follow-up asked by @JeroenDeDauw; diff not yet human-reviewed; mutants checked: an unregistered hook fails the save test and leaves MediaWiki:Maps unchanged, a dropped namespace check fails the renamed test; PHPUnit, phpcs and PHPStan pass locally.}