Fixes fulfillment notify_customer type

Author: sle-c

lib/shopify_api/rest/resources/2025_01/fulfillment.rb

@@ -63,7 +63,7 @@ def initialize(session: ShopifyAPI::Context.active_session, from_hash: nil)
     attr_reader :location_id
     sig { returns(T.nilable(String)) }
     attr_reader :name
-    sig { returns(T.nilable(Integer)) }
+    sig { returns(T.nilable(T::Boolean)) }
     attr_reader :notify_customer
     sig { returns(T.nilable(Integer)) }
     attr_reader :order_id