Backport to 18.9: Geo: Fix site validation when outbound request filtering is enabled

What does this MR do and why?

Backports severe bug Geo site URL is blocked when using outbound fil... (#544821) to current released version.

Configuring outbound filtering on Gitlab Dedicated causes issues with Geo region setup. The documentation explicitly states that Geo region will not be blocked, but it creates issues regardless. Adding the Geo region to outbound list fixes it. So Geo should be already added to outbound filtering, as the documentation states.

Related to Geo site URL is blocked when using outbound fil... (#544821)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• The MR title is descriptive (e.g. "Backport of 'title of default branch MR'"). This is important, since the title will be copied to the patch blog post.
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• Ensure the e2e:test-on-omnibus-ee job has succeeded, or if it has failed, investigate the failures. If you determine the failures are unrelated, you may proceed. If you need assistance investigating, reach out to a Software Engineer in Test in #s_developer_experience.

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