Keeping compat resources in a better-scoped path

Author: jglick

pipeline-model-definition/src/main/java/org/jenkinsci/plugins/pipeline/modeldefinition/Upgrade.java

@@ -100,7 +100,7 @@
             "org.jenkinsci.plugins.pipeline.modeldefinition.agent.impl.NoneScript");
         @Override public URL loadGroovySource(String clazz) {
             if (CLASSES.contains(clazz)) {
-                return Upgrade.class.getResource("/compat/" + clazz.replaceFirst(".+[.]", "") + ".groovy");
+                return Upgrade.class.getResource("compat/" + clazz.replaceFirst(".+[.]", "") + ".groovy");
             } else {
                 return null;
             }