chore(deps): bump boto3 in /lambda-powertools-feature-flags/app

Bumps [boto3](https://github.com/boto/boto3) from 1.28.76 to 1.35.78.
- [Release notes](https://github.com/boto/boto3/releases)
- [Commits](boto/boto3@1.28.76...1.35.78)

---
updated-dependencies:
- dependency-name: boto3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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