refactor: update typehints in workflows/cloud-client

[Sita04]

Description

b/280881575 : Update type hints in workflows/cloud-client.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• workflows/cloud-client/main.py:15, tag workflows_api_quickstart

You are about to delete 1 region tag.

• workflows/cloud-client/main.py:22, tag workflows_api_quickstart

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[kweinmeister]

Code looks good. Can you please add a Noxfile to enforce type hints? This will test your changes, and will ensure they are enforced in the future. Here's an example file which should work as-is.

[Sita04]

Done, thanks Karl.

[kweinmeister]

Code looks good. Can you please add a Noxfile to enforce type hints? This will test your changes, and will ensure they are enforced in the future. Here's an example file which should work as-is.

[engelke]

LGTM