Ban JUnit 4 imports (#473)

Author: strangelookingnerd

pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>5.20</version>
+    <version>5.21</version>
     <relativePath />
   </parent>
 
@@ -46,6 +46,7 @@
     <revision>2.22</revision>
     <changelist>-SNAPSHOT</changelist>
     <spotless.check.skip>false</spotless.check.skip>
+    <ban-junit4-imports.skip>false</ban-junit4-imports.skip>
   </properties>
 
   <dependencyManagement>