RFR: 8374655: Update CONTRIBUTING.md to ask PR authors to enable GHA in their repo

[Marius Hanl]

On Wed, 7 Jan 2026 00:13:45 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Adds a note to the "Testing" item for PR Authors to make sure that GHA is enabled for their personal fork. There is already a similar recommendation for Reviewers to check that.

As discussed, this a good enhancement.

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Marked as reviewed by mhanl (Committer).

PR Review: https://git.openjdk.org/jfx/pull/2028#pullrequestreview-3634348913