Fix nearestObjects position error

_pos should be _charPos. Currently it causes this error in server RPT on 1.63.112555+ because it references the player object, not the player object's position:

 6:36:48 Error in expression <ear"] call server_updateObject;
} count nearestObjects [_pos, dayz_updateObjects>
 6:36:48   Error position: <nearestObjects [_pos, dayz_updateObjects>
 6:36:48   Error 0 elements provided, 3 expected
 6:36:48 File z\addons\dayz_server\compile\server_playerSync.sqf, line 209