Upgrade Github actions

[markmur]

What are you trying to accomplish?

Upgrades Github actions to satisfy deprecation notice:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3, actions/setup-java@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/. 

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Before you merge

Testing

• I've added tests to support my implementation

Contribution guidelines

• I have read and agree with the Contribution Guidelines.
• I have read and agree with the Code of Conduct.

Documentation

• I've updated any documentation related to these changes.
• I've updated the README.

Versioning

• I have bumped the version number in the .podspec file.
• I have bumped the version number in the README.
• I have added a Changelog entry.

After merging

If your changes required a version bump, please add an entry under the Releases page - doing so will trigger a CI workflow to publish the latest Cocoapod.