Update conf.py

Author: xrmx

docs/conf.py

@@ -150,6 +150,10 @@
         "py:class",
         "opentelemetry.sdk.metrics._internal.aggregation._Aggregation",
     ),
+    (
+        "py:class",
+        "_contextvars:Token",
+    ),
 ]
 
 # Add any paths that contain templates here, relative to this directory.