Update copyright years to 2021.

Closes #616

neo4j/example/src/main/java/example/springdata/neo4j/Actor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2018 the original author or authors.
+ * Copyright 2015-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

neo4j/example/src/main/java/example/springdata/neo4j/ActorRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2018 the original author or authors.
+ * Copyright 2015-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,7 @@ public interface ActorRepository extends Neo4jRepository<Actor, Long> {
 
 	/**
 	 * Custom query to navigate over relationships with properties.
-	 * 
+	 *
 	 * @param title
 	 * @return
 	 */

neo4j/example/src/main/java/example/springdata/neo4j/Movie.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2020 the original author or authors.
+ * Copyright 2015-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

neo4j/example/src/main/java/example/springdata/neo4j/Roles.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2020 the original author or authors.
+ * Copyright 2015-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

neo4j/example/src/test/java/example/springdata/neo4j/ActorRepositoryIntegrationTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2020 the original author or authors.
+ * Copyright 2015-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.