JVMCI 20.3-b04 release

[Doug Simon]

The 20.3-b04 release includes:

	• GR-27026: Fix C2 crashes (JDK-8252904, JDK-8255466, JDK-8250825)
	• GR-24478: JVMCI should be more careful about reflective reads of Class.componentType.

The OpenJDK based Windows, Linux and macOS binaries are available at:

https://github.com/graalvm/graal-jvmci-8/releases/tag/jvmci-20.3-b04
https://github.com/graalvm/labs-openjdk-11/releases/tag/jvmci-20.3-b04
https://github.com/graalvm/labs-openjdk-15/releases/tag/jvmci-20.3-b04

-Doug