RFR: 8330569: Rename Nix to Posix in platform-dependent attachListener code

[Johan Sjölen]

Hi,

Revert the rename performed in 8324683.

Thanks.

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Commit messages:
 - Rename Nix to Posix in AttachListener

Changes: https://git.openjdk.org/jdk/pull/18836/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18836&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330569
  Stats: 28 lines in 1 file changed: 0 ins; 0 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/18836.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18836/head:pull/18836

PR: https://git.openjdk.org/jdk/pull/18836