Fix typing in metrictestutil.py

Author: jack-burridge-cfh

tests/opentelemetry-test-utils/src/opentelemetry/test/metrictestutil.py

@@ -40,7 +40,7 @@ def _generate_metric(
 
 def _generate_sum(
     name, value, attributes=None, description=None, unit=None
-) -> Sum:
+) -> Metric:
     if attributes is None:
         attributes = BoundedAttributes(attributes={"a": 1, "b": True})
     return _generate_metric(
@@ -64,7 +64,7 @@ def _generate_sum(
 
 def _generate_gauge(
     name, value, attributes=None, description=None, unit=None
-) -> Gauge:
+) -> Metric:
     if attributes is None:
         attributes = BoundedAttributes(attributes={"a": 1, "b": True})
     return _generate_metric(
@@ -86,7 +86,7 @@ def _generate_gauge(
 
 def _generate_unsupported_metric(
     name, attributes=None, description=None, unit=None
-) -> Sum:
+) -> Metric:
     return _generate_metric(
         name,
         None,