Bump @aws-sdk/client-cognito-identity-provider in /backend

Bumps [@aws-sdk/client-cognito-identity-provider](https://github.com/aws/aws-sdk-js-v3/tree/HEAD/clients/client-cognito-identity-provider) from 3.666.0 to 3.708.0.
- [Release notes](https://github.com/aws/aws-sdk-js-v3/releases)
- [Changelog](https://github.com/aws/aws-sdk-js-v3/blob/main/clients/client-cognito-identity-provider/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js-v3/commits/v3.708.0/clients/client-cognito-identity-provider)

---
updated-dependencies:
- dependency-name: "@aws-sdk/client-cognito-identity-provider"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>