RFR: 8258192: Obsolete the CriticalJNINatives flag

[Coleen Phillimore]

On Wed, 10 Nov 2021 22:06:05 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> This change removes the disabled CriticalJNINatives code, and the flag now gives an obsolete message.
> Tested with tier1 on cpus x64, aarch64, and builds on linux-x86-open,linux-s390x-open,linux-arm32-debug,linux-ppc64le-debug.

Thanks for reviewing, Aleksey.  I made the changes and will retest.

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PR: https://git.openjdk.java.net/jdk/pull/6343