Build: Bump mypy-boto3-dynamodb from 1.42.55 to 1.42.73

Bumps [mypy-boto3-dynamodb](https://github.com/youtype/mypy_boto3_builder) from 1.42.55 to 1.42.73.
- [Release notes](https://github.com/youtype/mypy_boto3_builder/releases)
- [Commits](https://github.com/youtype/mypy_boto3_builder/commits)

---
updated-dependencies:
- dependency-name: mypy-boto3-dynamodb
  dependency-version: 1.42.73
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]