[jdk22u] RFR: 8328604: remove on_aix() function

[Matthias Baesken]

8328604: remove on_aix() function

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Commit messages:
 - Backport 940d1965f831a9f7e4f1ce34e381c038827c7ca2

Changes: https://git.openjdk.org/jdk22u/pull/128/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk22u&pr=128&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328604
  Stats: 39 lines in 2 files changed: 0 ins; 30 del; 9 mod
  Patch: https://git.openjdk.org/jdk22u/pull/128.diff
  Fetch: git fetch https://git.openjdk.org/jdk22u.git pull/128/head:pull/128

PR: https://git.openjdk.org/jdk22u/pull/128