fix .__doc__ assignment for Callable type alias in exemplar_reservoir.py

Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>

Author: emdneto

opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/exemplar/exemplar_reservoir.py

@@ -318,9 +318,7 @@ def _find_bucket_index(
         return len(self._boundaries)
 
 
+# ExemplarReservoirBuilder: A callable that takes Aggregation parameters
+# (e.g. boundaries for _ExplicitBucketHistogramAggregation) and returns
+# an ExemplarReservoir instance.
 ExemplarReservoirBuilder = Callable[[dict[str, Any]], ExemplarReservoir]
-ExemplarReservoirBuilder.__doc__ = """ExemplarReservoir builder.
-
-It may receive the Aggregation parameters it is bounded to; e.g.
-the _ExplicitBucketHistogramAggregation will provide the boundaries.
-"""