build: replace upload-release-asset with action-gh-release

[tqpcharlie]

Summary:

This PR replaces the upload-release-asset action with action-gh-release, since the former has been deprecated for almost 5 years now. Fixes #2009

Expected behavior:

See the action-gh-release docs for info on my edits to the Action.

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[jcpitre]

@tqpcharlie Thanks for the contribution.
Since it's kind of difficult to test this unless we do an actual release, if you agree we will wait for the next release to merge this.

[tqpcharlie]

Hi all, reopened, sorry for the inconvenience

[Copilot]

Pull request overview

Updates the release publishing workflow to move away from the deprecated actions/upload-release-asset action and toward softprops/action-gh-release, aligning the repo’s release automation with currently maintained GitHub Actions.

Changes:

• Replaced the release-asset upload steps for the CLI and GUI JARs with softprops/action-gh-release@v2.
• Updated upload configuration to use files for artifact selection.

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[jcpitre]

@tqpcharlie We ran copilot on the changes and it pointed out some interesting issues.
We intend to release a new version shortly.
You could make the corrections yourself, or if it's not possible I can do them.
Let me know!

[jcpitre]

@tqpcharlie Thank you for the contribution!
We copied your branch into MobilityData/gtfs-validator so we could make some changes.
This means we needed a new PR: #2134
I am closing this PR since it's essentially replaced by #2134 .