Remove declaration of private/anonymous function

Never used outside objects.cpp so it was rightly moved into the anonymous namespace, but the header was not updated at the time.

Source/objects.cpp

@@ -3997,6 +3997,17 @@ void OperateWeaponRack(int pnum, int i, bool sendmsg)
 		NetSendCmdParam1(false, CMD_OPERATEOBJ, i);
 }
 
+/**
+ * @brief Checks whether the player is activating Na-Krul's spell tomes in the correct order
+ *
+ * Used as part of the final Diablo: Hellfire quest (from the hints provided to the player in the
+ * reconstructed note). This function both updates the state of the variable that tracks progress
+ * and also determines whether the spawn conditions are met (i.e. all tomes have been triggered
+ * in the correct order).
+ *
+ * @param s the id of the spell tome
+ * @return true if the player has activated all three tomes in the correct order, false otherwise
+ */
 bool OperateNakrulBook(int s)
 {
 	switch (s) {