RFR: 8339847: Broken link to the dieharder distribution website in SplittableRandom

[Nizar Benalla]

Could I get a review for this small change?
The page linked in `SplittableRandom` was moved at some point, this change points to the correct page to avoid redirects.

TIA

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Commit messages:
 - Broken link to the dieharder distribution website in SplittableRandom

Changes: https://git.openjdk.org/jdk/pull/21000/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21000&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339847
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21000.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21000/head:pull/21000

PR: https://git.openjdk.org/jdk/pull/21000