AO3-6870 Update proxy notice to include Russian, Ukranian translations

[slavalamp]

Pull Request Checklist

• Have you read "How to write the perfect pull request"?
• Have you read the contributing guidelines?
• Have you added tests for any changed functionality?
• Have you added the Jira issue number
  as the first thing in your pull request title (e.g. AO3-1234 Fix thing)
• Do you have fewer than 5 pull requests already open? If not, please wait
  until they are reviewed and merged before creating new pull requests.

Issue

https://otwarchive.atlassian.net/browse/AO3-6870

Purpose

Adds proxy notices in Russian and Ukrainian, which might be useful for proxies that seem to be designed to get around Russian blocks

Testing Instructions

See Jira issue

References

n/a

Credit

slavalamp (they/them)