chore: ban JUnit 4 imports (#369)

* Ban JUnit 4 imports

* Bump parent

Author: strangelookingnerd

pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>5.19</version>
+    <version>5.21</version>
   </parent>
 
   <artifactId>generic-webhook-trigger</artifactId>
@@ -61,6 +61,7 @@
     <violations.version>2.2.0</violations.version>
     <changelog>2.2.5</changelog>
     <spotless.check.skip>false</spotless.check.skip>
+    <ban-junit4-imports.skip>false</ban-junit4-imports.skip>
   </properties>
 
   <dependencyManagement>