[jdk17u-dev] RFR: 8378777: Bump update version for OpenJDK: jdk-17.0.20

[Goetz Lindenmaier]

Required version bump

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Commit messages:
 - 8378777: Bump update version for OpenJDK: jdk-17.0.20

Changes: https://git.openjdk.org/jdk17u-dev/pull/4281/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=4281&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378777
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/4281.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/4281/head:pull/4281

PR: https://git.openjdk.org/jdk17u-dev/pull/4281