[jdk17u-dev] RFR: 8286474: Drop --enable-preview from Sealed Classes related tests

[Goetz Lindenmaier]

I backport this for parity with 17.0.10-oracle.

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Commit messages:
 - Backport d547a707bf1f9e252213fdab7eaf076b5cf884b4

Changes: https://git.openjdk.org/jdk17u-dev/pull/1774/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1774&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286474
  Stats: 6 lines in 2 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1774.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1774/head:pull/1774

PR: https://git.openjdk.org/jdk17u-dev/pull/1774