[jdk19] RFR: 8291006: java/foreign/TestUnsupportedPlatform fails after JDK-8290455

[Maurizio Cimadamore]

This patch removes java/foreign/TestUnsupportedPlatform, which has been superseded by TestUnsupportedLinker, and is no longer required.
This old test relies on unspecified behavior and should be removed.

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Commit messages:
 - Drop TestUnsupportedPlatform test

Changes: https://git.openjdk.org/jdk19/pull/155/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=155&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291006
  Stats: 45 lines in 1 file changed: 0 ins; 45 del; 0 mod
  Patch: https://git.openjdk.org/jdk19/pull/155.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/155/head:pull/155

PR: https://git.openjdk.org/jdk19/pull/155