Fix errors in AWS Lambda examples

Author: seratch

examples/aws_lambda/aws_lambda.py

@@ -1,5 +1,7 @@
 import logging
+import sys
 
+sys.path.insert(1, "vendor")
 from slack_bolt import App
 from slack_bolt.adapter.aws_lambda import SlackRequestHandler
 

examples/aws_lambda/aws_lambda_oauth.py

@@ -1,4 +1,7 @@
 import logging
+import sys
+
+sys.path.insert(1, "vendor")
 
 from slack_bolt import App
 from slack_bolt.adapter.aws_lambda import SlackRequestHandler