[Security GenAI][AI Assistant] Remove ES|QL Query Generation quick prompt

[kyracho]

Summary

Hi 😊 this PR deals with #198630 .

It removes the ES|QL Query Generation quick prompt from the AI Assistant.

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• [n/a] Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• [n/a] Documentation was added for features that require explanation or tutorials
• [n/a] Unit or functional tests were updated or added to match the most common scenarios
• [n/a] If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• [n/a] This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• [n/a] Flaky Test Runner was used on any tests changed
• [n/a] The PR description includes the appropriate Release Notes section, and the correct release_node:* label is applied per the guidelines

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[stephmilovic]

@elasticmachine merge upstream

[stephmilovic]

I've included your commits in this PR which resolves the issue: #201276

I'm going to close your PR in favor of the new one. Thanks for contributing!