Delete Redundant Checkstyle Action from GitHub CI

[InsertCreativityHere]

We're currently running Checkstyle over the repo twice, once in the main java build, and another in a stand-alone checkstyle action. This PR deletes the standalone checkstyle action. There's no need to run it twice.

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Outdated:

We made this change in the main Ice repository, but I forgot to do the same for the demos.
See zeroc-ice/ice#4359

We have a separate action for running checkstyle, so we don't want the main Java build running it as well.

[Copilot]

Pull Request Overview

This PR modifies the CI workflow to disable checkstyle validation during Java demo builds by adding the -x checkStyleMain flag to the Gradle build command.

Key Change:

• Java demos now skip checkstyle validation during CI builds

[pepone]

I don't understand why we prefer this setup. To me seems more logical to keep the default and don't run checkStyle as a separate workflow.

[InsertCreativityHere]

I don't understand why we prefer this setup. To me seems more logical to keep the default and don't run checkStyle as a separate workflow.

I think it makes sense for Ice, where it's clearer to see the builds passed and only checkstyle failed,
as opposed to seeing every build failed.

For the demos, I'd be fine just getting rid of the checkstyle action and letting main CI handle it.
I just don't like that right now we're running it twice is all.

[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[InsertCreativityHere]

Reworked this PR to instead remove the checkstyle action.
Checkstyle is still run as part of the gradlew build process.