RFR: 8020199: (fs) Files.move() throws DirectoryNotEmptyException pointing to wrong directory (win)

[Brian Burkhalter]

Amend description of when `DirectoryNotEmptyException` is thrown by `Files::move`.

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Commit messages:
 - 8020199: (fs) Files.move() throws DirectoryNotEmptyException pointing to wrong directory (win)

Changes: https://git.openjdk.org/jdk/pull/15199/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15199&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8020199
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15199.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15199/head:pull/15199

PR: https://git.openjdk.org/jdk/pull/15199