update_matrix: Fix handling of data from postgres >= 14

With Postgresql 14, EXTRACT() function returns a numeric type instead of
a float. This is converted to a Decimal by asyncpg, thus breaking code
doing a sum of all ages.

Initialising the sum with 0 instead 0.0 fixes the issue.

control/insight.py

@@ -76,7 +76,7 @@ async def update_matrix(
     for analyser in matrix:
         min: Optional[float] = None
         max: Optional[float] = None
-        sum = 0.0
+        sum = 0
         for country in matrix[analyser]:
             v = matrix[analyser][country][0]
             min = v if not min or v < min else min