RFR: JDK-8309934: Update GitHub Actions to use JDK 17 for building jtreg

[Christian Stein]

Please review this change to use the pre-installed JDK 17 for building jtreg when running on GitHub Actions.

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Commit messages:
 - Use JDK 17 to build jtreg

Changes: https://git.openjdk.org/jdk/pull/14448/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14448&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309934
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14448.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14448/head:pull/14448

PR: https://git.openjdk.org/jdk/pull/14448