[foreign-jextract] RFR: 8260976: investigate ways to filter jextract output

[Maurizio Cimadamore]

This simple patch fixes a remaining use of `-Dforeign.restriced=permit` in the filter test.

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Commit messages:
 - Fix bad use of `-Dforeign.restriced=permit`

Changes: https://git.openjdk.java.net/panama-foreign/pull/493/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=493&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260976
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/493.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/493/head:pull/493

PR: https://git.openjdk.java.net/panama-foreign/pull/493