RFR: 8296618: Skip failing test SwingNodeDnDMemoryLeakTest until JDK-8285503 is fixed

[pandaapo]

Fixes [JDK-8296618](https://bugs.openjdk.org/browse/JDK-8296618)

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Commit messages:
 - Skip failing test SwingNodeDnDMemoryLeakTest until JDK-8285503 is fixed.

Changes: https://git.openjdk.org/jfx/pull/942/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=942&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296618
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/942.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/942/head:pull/942

PR: https://git.openjdk.org/jfx/pull/942