feat(CI): Added check for manual tests checkbox

[XrossFox]

Description

• Added GitHub Workflow that checks wether a user has performed a manual test.

Fixes b/519321791

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

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

[gemini-code-assist]

Code Review

This pull request updates the pull request template to recommend running local tests with Python 3.10 instead of Python 3.9. The reviewer recommends keeping the test command set to Python 3.9 to ensure compatibility with the minimum supported Python version and to prevent contributors from introducing incompatible Python 3.10+ features.

[gemini-code-assist]

According to the AUTHORING_GUIDE.md (line 112), Python 3.9 is still a supported version ("Samples should support Python 3.9, 3.10, 3.11, 3.12 and 3.13."). Changing the recommended local test command to py-3.10 might lead contributors to use Python 3.10+ features (such as the union operator | for types) that are incompatible with Python 3.9. It is safer to keep the test command as py-3.9 to ensure compatibility with the minimum supported version.

Suggested change

	- [ ] **Tests** pass: `nox -s py-3.10` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))
	- [ ] **Tests** pass: `nox -s py-3.9` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))