Fix anonymouseditwarning message key

so it says "item's edit history" instead of "property's edit history"

Change-Id: I16fe727116c64360a7abd02d635c3a7b1fb51230
remove $wgUser global and get user from context

Change-Id: Ic48ae0a72ee527a44c914558be0de20329f575c7
Merge changes Ic48ae0a7,I16fe7271

* changes:
  remove $wgUser global and get user from context
  Fix anonymouseditwarning message key