testing/openjdk15: upgrade to 15.0.4
This MR upgrades jdk15 to the latest release, fixing many issues:
https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2021-July/006956.html
Edited by Simon F
This MR upgrades jdk15 to the latest release, fixing many issues:
https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2021-July/006956.html