[jdk18] RFR: 8279195: Document the -XX:+NeverActAsServerClassMachine flag

[Vladimir Kozlov]

This product flag provides a way to emulate the old "Client VM" but has never been documented in the java command reference (aka manpage). It should be documented.

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Commit messages:
 - 8279195: Document the -XX:+NeverActAsServerClassMachine flag

Changes: https://git.openjdk.java.net/jdk18/pull/71/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18&pr=71&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279195
  Stats: 25 lines in 1 file changed: 25 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk18/pull/71.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18 pull/71/head:pull/71

PR: https://git.openjdk.java.net/jdk18/pull/71