Apply suggestions from code review

Co-authored-by: Emídio Neto <[email protected]>

Author: xrmx

opentelemetry-api/src/opentelemetry/context/__init__.py

@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 import logging
 import typing
 from contextvars import Token

opentelemetry-api/src/opentelemetry/context/context.py

@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 import typing
 from abc import ABC, abstractmethod
 from contextvars import Token

opentelemetry-api/src/opentelemetry/context/contextvars_context.py

@@ -11,6 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+from __future__ import annotations
+
 from contextvars import ContextVar, Token
 
 from opentelemetry.context.context import Context, _RuntimeContext