[a11y] Fix focus on generate API keys in connectors config

[dennis-tismenko]

Summary

Closes #200028.

Resolves an accessibility issue where opening the modal to generate API keys on the content connectors configuration page would incorrectly return focus to the top of the page after the confirmation modal closes.

Before

Screen.Recording.2025-10-03.at.1.58.32.PM.mov

After

Screen.Recording.2025-10-03.at.1.57.49.PM.mov

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• 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.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.

[elasticmachine]

💔 Build Failed

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• Commit: f7fd83a

Failed CI Steps

[dennis-tismenko]

@elasticmachine merge upstream