fixed year in javadoc

Author: nulls

plugin-maven/src/main/java/com/diffplug/spotless/maven/kotlin/Diktat.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021 DiffPlug
+ * Copyright 2021-2022 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,8 +15,6 @@
  */
 package com.diffplug.spotless.maven.kotlin;
 
-import java.util.Collections;
-
 import org.apache.maven.plugins.annotations.Parameter;
 
 import com.diffplug.spotless.FileSignature;