[jdk25u] RFR: 8369078: Fix faulty test conversion in IllegalCharsetName.java

[duke]

On Fri, 10 Oct 2025 18:15:50 GMT, Justin Lu <jlu at openjdk.org> wrote:

> A test-only correction, which is a backport of commit [0f406c42](https://github.com/openjdk/jdk/commit/0f406c420e35f7a4358dc99711fd23d162f21777) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

@justin-curtis-lu 
Your change (at version 1d1e06b59a0fb1d3917f47c51541b5fd3b4b789f) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk25u/pull/293#issuecomment-3398163885