DATACMNS-1755 - Fix malformed copyright headers.

Fix a few copyright headers that had formatting or date issues.

Original pull request: #448.

src/main/java/org/springframework/data/mapping/model/MutablePersistentEntity.java

@@ -1,11 +1,11 @@
 /*
- * Copyright 2011-2020 the original authors.
+ * Copyright 2011-2020 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.
  * You may obtain a copy of the License at
  *
- *     https://www.apache.org/licenses/LICENSE-2.0
+ *      https://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,