fix(retail): add region tag for Python - search with query expansion spec

[rebeccaellis]

Description

Fixes #415382524

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

[snippet-bot[bot]]

Here is the summary of changes.

You are about to add 1 region tag.

• retail/interactive-tutorials/search/search_with_query_expansion_spec.py:18, tag retail_search_for_products_with_query_expansion_specification

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[glasnt]

This PR is failing in similar ways as reported in https://github.com/GoogleCloudPlatform/nodejs-docs-samples/issues/4136

This is the last PR in this batch left, so isn't blocking any other PR, so should be addressed directly.