[jdk11u-dev] RFR: 8309934: Update GitHub Actions to use JDK 17 for building jtreg

[George Adams]

Makes sense to be consistent with newer versions, applies cleanly

-------------

Commit messages:
 - Backport 8aad881e803fddc26f45270f779ff0c0e5a095d8

Changes: https://git.openjdk.org/jdk11u-dev/pull/2845/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2845&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309934
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2845.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2845/head:pull/2845

PR: https://git.openjdk.org/jdk11u-dev/pull/2845