chore(datalabeling): remove decommissioned samples and unused region tags

[angelcaamal]

Description

Removes the decommissioned datalabeling samples and directory.

The Cloud Data Labeling API has been turned down, causing integration tests to fail with 502 Bad Gateway and DEADLINE_EXCEEDED timeouts as the backend is no longer active.

Region Tags

• Removed decommissioned and unused region tag: [START datalabeling_quickstart] / [END datalabeling_quickstart]
  Fixes b/558837315

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

Checklist

• I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• Tests pass: npm test (see Testing)
• Lint pass: npm run lint (see Style)
• Required CI tests pass (see CI testing)
• 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 pull request is from a branch created directly off of GoogleCloudPlatform/nodejs-docs-samples. Not a fork.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new sample directory, and I created GitHub Actions workflow 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

Note: Any check with (dev), (experimental), or (legacy) can be ignored and should not block your PR from merging (see CI testing).

[gemini-code-assist]

Code Review

This pull request removes all files from the project, including the configuration files, README documentation, package.json, the quickstart sample script, and its associated tests. I have no feedback to provide as there are no active review comments.

[Kef131]

No references on devsite

[XrossFox]

LGTM