RFR: 8350654: (fs) Files.createTempDirectory should say something about the default file permissions when no file attributes specified

[Brian Burkhalter]

Add a sentence clarifying the behavior of `Files.createTempDirectory(Path,String,FileAttribute<?>...)` when no attributes are specified.

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Commit messages:
 - 8350654: (fs) Files.createTempDirectory should say something about the default file permissions when no file attributes specified

Changes: https://git.openjdk.org/jdk/pull/23808/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23808&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350654
  Stats: 5 lines in 1 file changed: 3 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23808.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23808/head:pull/23808

PR: https://git.openjdk.org/jdk/pull/23808