RFR: 8372307: Clean up the leftover code comment references to file.encoding in java_props_md.c

[Roger Riggs]

On Fri, 29 Aug 2025 14:25:25 GMT, Igor Rudenko <duke at openjdk.org> wrote:

> The `file.encoding` system property is no longer used by the JDK.
> Updated code comments to reference the correct replacement: `native.encoding`.

You may find it useful to read the [OpenJDK Developers Guide](https://openjdk.org/guide/#contributing-to-an-openjdk-project).

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PR Comment: https://git.openjdk.org/jdk/pull/27004#issuecomment-3563759311