RFR: 8525: Update 9.1 splash copyright year

[Marcus Hirt]

Updating the copyright year for the 9.1.2 release.

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Commit messages:
 - 8525: Update 9.1 splash copyright year

Changes: https://git.openjdk.org/jmc/pull/703/files
  Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=703&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8525
  Stats: 0 lines in 1 file changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jmc/pull/703.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/703/head:pull/703

PR: https://git.openjdk.org/jmc/pull/703