Remove context manager check (open-telemetry#2391)

Author: lzchen

.pylintrc

@@ -81,6 +81,7 @@ disable=missing-docstring,
       missing-module-docstring, # temp-pylint-upgrade
       import-error, # needed as a workaround as reported here: https://github.com/open-telemetry/opentelemetry-python-contrib/issues/290
       cyclic-import,
+      not-context-manager
 
 # Enable the message, report, category or checker with the given id(s). You can
 # either give multiple identifier separated by comma (,) or put this option