Remove debug assert after picking up an item

Doesn't really do anything useful. If the target position doesn't contain an item on the local client the code looks for a matching dropped item and tries to pick that up instead. It doesn't really make sense to assert that an item exists at the target position or that it matches, a desync has already happened by this point if the checks on lines 1647 or 1649 are false.

Source/inv.cpp

@@ -1661,7 +1661,6 @@ void SyncGetItem(Point position, int idx, uint16_t ci, int iseed)
 		return;
 
 	CleanupItems(&Items[ii], ii);
-	assert(FindGetItem(idx, ci, iseed) == -1);
 }
 
 bool CanPut(Point position)