dependency: bump maven-source-plugin in /sevntu-checkstyle-sonar-plugin

Bumps [maven-source-plugin](https://github.com/apache/maven-source-plugin) from 2.2.1 to 3.2.1.
- [Release notes](https://github.com/apache/maven-source-plugin/releases)
- [Commits](apache/maven-source-plugin@maven-source-plugin-2.2.1...maven-source-plugin-3.2.1)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-source-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

sevntu-checkstyle-sonar-plugin/pom.xml

@@ -66,7 +66,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>
-        <version>2.2.1</version>
+        <version>3.2.1</version>
         <executions>
           <execution>
             <id>attach-sources</id>