[foreign-memaccess+abi] RFR: 8264422: SpliteratorTest fails after ResourceScope integration

[Maurizio Cimadamore]

This simple fix adapts SpliteratorTest to use a try-with-resources block against a ResourceScope, and not against a MemorySegment directly.

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Commit messages:
 - 8264422: SpliteratorTest fails after ResourceScope integration

Changes: https://git.openjdk.java.net/panama-foreign/pull/482/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=482&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264422
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/482.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/482/head:pull/482

PR: https://git.openjdk.java.net/panama-foreign/pull/482