RFR: 8322321: Add man page doc for -XX:+VerifySharedSpaces

[Ioi Lam]

`VerifySharedSpaces` was disabled in [JDK-8221478](https://bugs.openjdk.org/browse/JDK-8221478) by default. We should add an entry in the "java" man page about the intended use for this flag.

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Commit messages:
 - 8322321: Add man page doc for -XX:+VerifySharedSpaces

Changes: https://git.openjdk.org/jdk/pull/17152/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17152&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322321
  Stats: 9 lines in 1 file changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17152.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17152/head:pull/17152

PR: https://git.openjdk.org/jdk/pull/17152