RFR: 8345164: Remove residual --enable-preview in FFM tests and benchmarks

[Maurizio Cimadamore]

On Tue, 3 Dec 2024 12:01:42 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> This PR proposes to remove redundant `--enable-preview` flags in a test and a benchmark.

Marked as reviewed by mcimadamore (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/22512#pullrequestreview-2475493993