Incorrect capitalization in Arrays.compare and Arrays.mismatch Javadocs

[Eirik Bjørsnøs]

Please review this documentation-only change which fixes incorrect
capitalization when referencing "aToIndex" and "bToIndex" in the Javadocs
of Arrays.compare and Arrays.mismatch.

https://github.com/openjdk/jdk/pull/12488

Thanks,
Eirik.