RFR: 8351349: GSSUtil.createSubject has outdated access control context and policy related text

[Sean Mullan]

Please review this change to remove outdated access control context and policy related text from the `com.sun.security.jgss.GSSUtil` class which no longer applies now that JEP 486 disabled the Security Manager. I have removed the text and not tried to replace it. I think it is better to keep the method description simple and not assume what a server might do with the subject, such as using it to impersonate a client.

I also made a few other minor changes, adding code tags around class names and changing "Sun Microsystem's" to "the JDK" in the class description.

I will also file a CSR.

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Commit messages:
 - Initial changes.

Changes: https://git.openjdk.org/jdk/pull/23970/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23970&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351349
  Stats: 26 lines in 1 file changed: 1 ins; 4 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/23970.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23970/head:pull/23970

PR: https://git.openjdk.org/jdk/pull/23970