Bump spotless-maven-plugin from 2.1.0 to 2.3.1

Bumps [spotless-maven-plugin](https://github.com/diffplug/project) from 2.1.0 to 2.3.1.
- [Release notes](https://github.com/diffplug/project/releases)
- [Commits](https://github.com/diffplug/project/commits)

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

Author: dependabot[bot]

pom.xml

@@ -334,7 +334,7 @@
       <plugin>
         <groupId>com.diffplug.spotless</groupId>
         <artifactId>spotless-maven-plugin</artifactId>
-        <version>2.1.0</version>
+        <version>2.3.1</version>
         <configuration>
           <formats>
             <format>