Chore [deps:npm]: bump @aws-sdk/rds-signer from 3.758.0 to 3.856.0

Bumps [@aws-sdk/rds-signer](https://github.com/aws/aws-sdk-js-v3/tree/HEAD/packages/rds-signer) from 3.758.0 to 3.856.0.
- [Release notes](https://github.com/aws/aws-sdk-js-v3/releases)
- [Changelog](https://github.com/aws/aws-sdk-js-v3/blob/main/packages/rds-signer/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js-v3/commits/v3.856.0/packages/rds-signer)

---
updated-dependencies:
- dependency-name: "@aws-sdk/rds-signer"
  dependency-version: 3.856.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]