RFR: 8296153: Bump minimum boot jdk to JDK 20

Fri Apr 21 18:19:41 UTC 2023

On Thu, 20 Apr 2023 19:15:00 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> With the JDK 20 GA out it's time to bump the minimum boot JDK version for mainline/JDK 21.
> 
> Testing: tier1-5, GHA (the Windows build successfully downloads the JDK but then fails for unrelated reasons, and one seemingly unrelated Vector API test failure in tier 3)

Marked as reviewed by darcy (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/13565#pullrequestreview-1396221320