[foreign-abi] RFR: 8250798: [Test] Cleanup @modules jtreg directives for jdk_foreign tests

[Henry Jen]

@module jdk.incubator.foreign is not needed as that's specified in test/jdk/java/foreign/TEST.properties.
Remove directives to export unused internal API.

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Commit messages:
 - Cleanup @modules tags for jdk_foreign tests

Changes: https://git.openjdk.java.net/panama-foreign/pull/274/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/274/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8250798
  Stats: 35 lines in 13 files changed: 0 ins; 32 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/274.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/274/head:pull/274

PR: https://git.openjdk.java.net/panama-foreign/pull/274