Add europe-west1 region to GCP list in eis.md

[seanhandley]

Summary

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

🔍 Preview links for changed docs

• explore-analyze/elastic-inference/eis.md

[github-actions]

Vale Linting Results

Summary: 2 suggestions found

💡 Suggestions (2)

File	Line	Rule	Message
explore-analyze/elastic-inference/eis.md	78	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
explore-analyze/elastic-inference/eis.md	78	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.

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