RFR: 8339017: Make a couple of fields in DoubleByte static

[Brian Burkhalter]

On Thu, 25 Jul 2024 11:42:58 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

> 3 fields in `sun.nio.cs.DoubleByte.{Encoder,Decoder}` could be made 'static':
> 1. SS2
> 2. SS3
> 3. MAX_SINGLEBYTE

Looks all right but I think @naotoj might like to review it as well.

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Marked as reviewed by bpb (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20329#pullrequestreview-2261800387