RFR: 8240832: Remove unused applecoreaudio.md third-party legal file

[Kevin Rushforth]

As noted in the JBS issue, this is a follow-on bug to
[https://bugs.openjdk.java.net/browse/JDK-8232589](https://bugs.openjdk.java.net/browse/JDK-8232589) to remove the
applecoreaudio.md third-party legal file now that we no longer include or use CoreAudio.

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Commit messages:
 - 8240832: Remove unused applecoreaudio.md third-party legal file

Changes: https://git.openjdk.java.net/jfx/pull/142/files
 Webrev: https://webrevs.openjdk.java.net/jfx/142/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8240832
  Stats: 53 lines in 1 file changed: 0 ins; 53 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/142.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/142/head:pull/142

PR: https://git.openjdk.java.net/jfx/pull/142