chore(deps): bump boto3 from 1.18.1 to 1.18.15

Bumps [boto3](https://github.com/boto/boto3) from 1.18.1 to 1.18.15.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](boto/boto3@1.18.1...1.18.15)

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

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

Author: dependabot[bot]