Use add_expansions_to_env

Author: NoahStapp

.evergreen/config.yml

@@ -796,7 +796,6 @@ functions:
 
           # This is required for pypy3.7 UTF encoding
           export LC_ALL=en_US.UTF-8
-          source ${PROJECT_DIRECTORY}/prepare_aws_connection.sh
           bash ${PROJECT_DIRECTORY}/.evergreen/tox.sh ${PYTHON_BINARY} -m aws-secrets -- drivers/test
 
     - command: expansions.update