zero capacity firm should also be removed from candidate list to prevent repeated request

firm.py

@@ -246,6 +246,15 @@ class FirmAgent(ap.Agent):
                             select_customer = \
                                 self.model.nprandom.choice(lst_firm_connect)
                         self.accept_request(select_customer, product)
+            else:
+                for down_firm in lst_firm:
+                    down_firm.dct_cand_alt_supp_up_prod_disrupted[
+                        product].remove(self)
+
+                    print(
+                        f"{self.name} denied {product.code} request "
+                        f"from {down_firm.name} for lack of capacity"
+                    )
 
     def accept_request(self, down_firm, product):
         # para product is the product that self is selling