add comment for lambda constants

Author: yiyuan-he

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/_aws_metric_attribute_generator.py

@@ -103,6 +103,7 @@
 _NORMALIZED_LAMBDA_SERVICE_NAME: str = "AWS::Lambda"
 _DB_CONNECTION_STRING_TYPE: str = "DB::Connection"
 
+# Constants for Lambda operations
 _LAMBDA_APPLICATION_SIGNALS_REMOTE_ENVIRONMENT: str = "LAMBDA_APPLICATION_SIGNALS_REMOTE_ENVIRONMENT"
 _LAMBDA_INVOKE_OPERATION: str = "Invoke"