[Security] Workflow update.yml is using vulnerable action actions/checkout

The workflow update.yml is referencing action actions/checkout using references v1. However this reference is missing the commit [a6747255bd19d7a757dbdda8c654a9f84db19839](https://github.com/actions/checkout/commits/a6747255bd19d7a757dbdda8c654a9f84db19839) which may contain fix to the some vulnerability.
The vulnerability fix that is missing by actions version could be related to:
(1) CVE fix
(2) upgrade of vulnerable dependency
(3) fix to secret leak and others.
Please consider to update the reference to the action.

Open update.yml and inspect its actions/checkout reference, which currently uses v1. Review the linked commit a6747255bd19d7a757dbdda8c654a9f84db19839 and update the workflow reference accordingly. Done means update.yml no longer uses the vulnerable reference and points to the requested fixed revision.

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