[jdk19] RFR: 8289930: Improve Thread description of inherited AccessControlContext

[Alan Bateman]

This is javadoc only change. The "Inheritance when creating threads" section in the Thread description lists the things that are inherited when creating a Thread. This includes the somewhat obscure "inherited AccessControlContext" where the first sentence looks like it wants to be a heading. The proposal change is tiny, it stops the first sentence/prefix "Inherited Access Control Context:"  and replaces it with the sentence "The captured caller context is the new thread's inherited AccessControlContext".  When the legacy SecurityManager is degraded further then I expect this paragraph will be removed. 

No semantic changes and I think below the radar for needing a csr.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk19/pull/121/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=121&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289930
  Stats: 7 lines in 1 file changed: 1 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk19/pull/121.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/121/head:pull/121

PR: https://git.openjdk.org/jdk19/pull/121