Fix test failing on <= 3.8

Author: aabmass

exporter/opentelemetry-exporter-otlp-proto-common/src/opentelemetry/exporter/otlp/proto/common/_internal/__init__.py

@@ -13,6 +13,8 @@
 # limitations under the License.
 
 
+from __future__ import annotations
+
 import logging
 from collections.abc import Sequence
 from itertools import count