Add NINETEEN to JavaVersion enum

[pruidong]

I prepared a PR for this. But when running the tests, I found that junit needs to be upgraded to 5.9.0, in order for the tests to work (Spring Boot currently depends on junit 5.8.2).

Please what can I do for this? Thanks.

[pruidong]

junit JRE.java:

https://github.com/junit-team/junit5/blob/r5.9.0/junit-jupiter-api/src/main/java/org/junit/jupiter/api/condition/JRE.java#L131