Ban JUnit 4 imports (jenkinsci#121)

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>
     <relativePath />
   </parent>
 
@@ -56,6 +56,7 @@
     <jenkins.version>${jenkins.baseline}.3</jenkins.version>
     <gitHubRepo>jenkinsci/${project.artifactId}-plugin</gitHubRepo>
     <mockserver.version>5.15.0</mockserver.version>
+    <ban-junit4-imports.skip>false</ban-junit4-imports.skip>
   </properties>
 
   <dependencyManagement>