DATAMONGO-2509 - Polishing.

Fix typos, improve wording. Reworks documentation specific to MongoDB 3 and 4.

Original pull request: #853.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/util/json/package-info.java

@@ -1,19 +1,3 @@
-/*
- * Copyright 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
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
 /**
  * MongoDB driver-specific utility classes for Json conversion.
  */