Bump junit in /jigsaw-examples/example_maven-project/src/modmain

Bumps [junit](https://github.com/junit-team/junit4) from 4.12 to 4.13.1.
- [Release notes](https://github.com/junit-team/junit4/releases)
- [Changelog](https://github.com/junit-team/junit4/blob/main/doc/ReleaseNotes4.12.md)
- [Commits](junit-team/junit4@r4.12...r4.13.1)

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

Author: dependabot[bot]

jigsaw-examples/example_maven-project/src/modmain/pom.xml

@@ -23,7 +23,7 @@
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>4.12</version>
+      <version>4.13.1</version>
       <scope>test</scope>
     </dependency>
   </dependencies>