RFR: 8344949: javax.security.auth.Subject.SecureSet.writeObject does not do a security check anymore

[Sean Mullan]

The Serial Data section of `javax.security.auth.Subject.SecureSet.writeObject()` should be removed as it no longer does a security check now that the Security Manager is permanently disabled.

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Commit messages:
 - Remove serialData text.

Changes: https://git.openjdk.org/jdk/pull/22390/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22390&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344949
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22390.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22390/head:pull/22390

PR: https://git.openjdk.org/jdk/pull/22390