RFR: 8315563: Remove references to JDK-8226420 from problem list

[Kevin Walls]

On Sat, 2 Sep 2023 00:50:08 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

> JDK-8226420 has been closed as a duplicate.
> The fix removes references to 8226420 from problemlist (the tests remain problem-listed due other issues).

Marked as reviewed by kevinw (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/15548#pullrequestreview-1608988502