RFR: 8357401: BigDecimal: Constants ONE_TENTH and ONE_HALF are unused after JDK-8341402

[Sergey Bylokhov]

Both fields were added by the [JDK-4851777](https://bugs.openjdk.org/browse/JDK-4851777):
see https://github.com/openjdk/jdk/commit/4045a8be07195acac7fb2faef0e6bf90edcaf9f8
And the usage were deleted by the [JDK-8341402](https://bugs.openjdk.org/browse/JDK-8341402):
see https://github.com/openjdk/jdk/commit/c4c3edfa964ef504f12971c5deef7c7355bdf325

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Commit messages:
 - Merge branch 'openjdk:master' into bigd
 - unused ONE_TENTH and ONE_HALF

Changes: https://git.openjdk.org/jdk/pull/25339/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25339&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357401
  Stats: 10 lines in 1 file changed: 0 ins; 10 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25339.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25339/head:pull/25339

PR: https://git.openjdk.org/jdk/pull/25339