fix: fixed types in new protocol

Author: bm424

sourcery_analytics/metrics/compounders.py

@@ -10,7 +10,7 @@
 U = typing.TypeVar("U")
 
 
-class Compounder(typing.Protocol[N, T]):
+class Compounder(typing.Protocol[N, T, U]):
     def __call__(self, *metrics: Metric[N, T]) -> Metric[N, U]:
         ...