hg: jdk/submit: 8246222: Rename javac test T6395981.java to be more informative

[joe.darcy at oracle.com]

Changeset: 62b2b2dd04d4
Author:    darcy
Date:      2020-06-12 13:16 -0700
URL:       https://hg.openjdk.java.net/jdk/submit/rev/62b2b2dd04d4

8246222: Rename javac test T6395981.java to be more informative
Reviewed-by: jjg

- test/langtools/tools/javac/api/T6395981.java
+ test/langtools/tools/javac/api/TestGetSourceVersions.java