Bump junit from 4.12 to 4.13.1

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]

cf-java-monitoring-custom-metrics-clients/pom.xml

@@ -43,7 +43,7 @@
             <dependency>
                 <groupId>junit</groupId>
                 <artifactId>junit</artifactId>
-                <version>4.12</version>
+                <version>4.13.1</version>
                 <scope>test</scope>
             </dependency>
             <dependency>

pom.xml

@@ -174,7 +174,7 @@
         <source.plugin.version>3.2.1</source.plugin.version>
         <jar.plugin.version>3.2.0</jar.plugin.version>
         <hamcrest.version>1.3</hamcrest.version>
-        <junit.version>4.12</junit.version>
+        <junit.version>4.13.1</junit.version>
         <mockito.version>1.9.5</mockito.version>
         <surefire.plugin.version>2.18.1</surefire.plugin.version>
         <animal.sniffer.version>1.18</animal.sniffer.version>