message: docs: update contributor instructions for installing java
  For angular contributors, updates the instructions for installing java
  in the DEVELOPER.md. Adds more details about which version of java is
  requried, and what uses java.
  Resolves
  PR Close
diff: @@ -29,8 +29,7 @@ following products on your development machine:
  * [Yarn](https://yarnpkg.com) (version specified in the engines field of [`package.json`](../package.json)) which is used to install dependencies.
  -* [Java Development Kit](https://www.oracle.com/technetwork/java/javase/downloads/index.html) which is used
  - to execute the selenium standalone server for e2e testing.
  +* Optional: [Java](https://openjdk.java.net/) version 7 or higher as required by [Closure Compiler](https://developers.google.com/closure/compiler). Most developers will not need this. Java is required for running some of the integration tests.
  ## Getting the Sources
  