* Revert "Change robots.txt to exclude some URLs (#10037)"

This reverts commit 80161f4351.

* Let's block media_proxy

/media_proxy/ is a dynamic route used for requesting uncached media, so it's
probably bad to let crawlers use it

* misleading comment

- Exclude static assets
- Exclude uploaded files
- Exclude alternate versions of the profile page
- Exclude media proxy URLs