[jdk21u-dev] RFR: 8378775: Bump update version for OpenJDK: jdk-21.0.12

[Goetz Lindenmaier]

Required version bump.

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Commit messages:
 - 8378775: Bump update version for OpenJDK: jdk-21.0.12

Changes: https://git.openjdk.org/jdk21u-dev/pull/2641/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2641&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378775
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2641.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2641/head:pull/2641

PR: https://git.openjdk.org/jdk21u-dev/pull/2641