Bump boto3 from 1.11.9 to 1.12.2 in /backend/uclapi
Bump boto3 from 1.11.9 to 1.12.2 in /backend/uclapi

Bumps [boto3](https://github.com/boto/boto3) from 1.11.9 to 1.12.2.
- [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/1.11.9...1.12.2)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
uclapi/uclapi,uclapi/uclapi,uclapi/uclapi,uclapi/uclapi