api: align argument with implementations

The two implementations have no stars,
so remove the stars on the abstract
method as well.

Author: pjonsson

cubedash/index/api.py

@@ -102,7 +102,7 @@ def put_summary(self, product_id: int, start_day, period, summary_row: dict): ..
     def product_summary_cols(self, product_name: str): ...
 
     @abstractmethod
-    def upsert_product_record(self, product_name: str, **fields): ...
+    def upsert_product_record(self, product_name: str, fields): ...
 
     @abstractmethod
     def upsert_product_regions(self, product_id: int): ...