Fix interpretation of 'prioritized'
Fix interpretation of 'prioritized'

Docs (especially in EventPresentationModel.php) say true means outside
the menu, false inside.

However, it was interpreting any non-undefined value as true.

Change-Id: Icb438538e5c588c1ac7d4bbac0b762dd07057199

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo