use plugins manager

Author: FinlayRJW

gradle-palantir-java-format/src/main/groovy/com/palantir/javaformat/gradle/PalantirJavaFormatIdeaPlugin.java

@@ -62,7 +62,7 @@ public void apply(Project rootProject) {
             configureIntelliJImport(rootProject, implConfiguration, nativeImplConfiguration);
         });
 
-        rootProject.getPlugins().apply(IdeaConfigurationPlugin.class);
+        rootProject.getPluginManager().apply(IdeaConfigurationPlugin.class);
 
         IdeaConfigurationExtension extension = rootProject.getExtensions().getByType(IdeaConfigurationExtension.class);