[l10n] Improve Russian (ru-RU) locale

[vasiljevdenis]

• I have followed (at least) the PR section of the contributing guide.

[mui-bot]

Localization writing tips ✍️

Seems you are updating localization 🌍 files.

Thank you for contributing to the localization! 🎉 To make your PR perfect, here is a list of elements to check: ✔️

• Verify if the PR title respects the release format. Here are two examples (depending if you update or add a locale file)

  [l10n] Improve Swedish (sv-SE) locale
  [l10n] Add Danish (da-DK) locale

• Update the documentation of supported locales by running pnpm l10n
• Clean files with pnpm prettier.

Deploy preview: https://deploy-preview-16591--material-ui-x.netlify.app/

Generated by 🚫 dangerJS against 3f71887

[vasiljevdenis]

The locale is fully translated

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.