Bump boto3 from 1.17.54 to 1.17.56
Bump boto3 from 1.17.54 to 1.17.56

Bumps [boto3](https://github.com/boto/boto3) from 1.17.54 to 1.17.56.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](https://github.com/boto/boto3/compare/1.17.54...1.17.56)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
DemocracyClub/UK-Polling-Stations,DemocracyClub/UK-Polling-Stations,DemocracyClub/UK-Polling-Stations