Update Step3.en.md

[brentroady]

Python runtime given throws an exception when creating the lambda function (InvalidParameterValueException). Update to the new runtime version.

Issue #, if available:

Description of changes:
Running the lamba create-function results in the following error

:~/workshop $ aws lambda create-function \
--function-name ddbreplica_lambda --zip-file fileb://ddbreplica_lambda.zip \
--handler ddbreplica_lambda.lambda_handler --timeout 60 --runtime python3.7 \
--description "Sample lambda function for dynamodb streams" \
--role $(cat ~/workshop/ddb-replication-role-arn.txt)

An error occurred (InvalidParameterValueException) when calling the CreateFunction operation: The runtime parameter of python3.7 is no longer supported for creating or updating AWS Lambda functions. We recommend you use the new runtime (python3.12) while creating or updating functions.

This change updates the example to use the recommended Python runtime.

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[switch180]

Thank you for finding this and reporting it. We will add to this commit some other changes for the lab guide and merge it in.