Bump maven-checkstyle-plugin from 2.7 to 3.1.1

Bumps [maven-checkstyle-plugin](https://github.com/apache/maven-checkstyle-plugin) from 2.7 to 3.1.1.
- [Release notes](https://github.com/apache/maven-checkstyle-plugin/releases)
- [Commits](https://github.com/apache/maven-checkstyle-plugin/compare/maven-checkstyle-plugin-2.7...maven-checkstyle-plugin-3.1.1)

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