Chore [deps:npm]: Bump @aws-sdk/rds-signer from 3.713.0 to 3.715.0

Bumps [@aws-sdk/rds-signer](https://github.com/aws/aws-sdk-js-v3/tree/HEAD/packages/rds-signer) from 3.713.0 to 3.715.0.
- [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/v3.715.0/packages/rds-signer)

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

Signed-off-by: dependabot[bot] <[email protected]>