Remove references to RuntimePermission("stopThread") from security docs

RuntimePermission("stopThread") has been removed, so all references to it from security docs should also be removed. For example:

1. https://docs.oracle.com/en/java/javase/19/security/permissions-jdk1.html#GUID-8B521D4F-1502-42EA-BA70-8E3322A163B5 (search for “stopThread”). The 3 rows should be removed.

Thread.stop(Throwable) was actually removed in a previous release, and ThreadGroup.stop() was degraded in 19 to throw UOE, so this is extra cleanup that should have been done already.

2. https://docs.oracle.com/en/java/javase/19/security/java-se-platform-security-architecture.html#GUID-744ACFDF-6ED1-473D-9D3A-5F34541A4377

Remove "stopThread" line.