[Tails-dev] [review'n'merge] Remove obsolete issue

Hello, an issue in Known issues page is obsolete:
https://tails.boum.org/support/known_issues/index.en.html#index40h2
Search engine has switch to DDG a year ago (#11913) and with security
slider set to High, DDG automatically redirect to the version without
JavaScript (no click required).

Please review and merge.

Repo: https://git-tails.immerda.ch/xin/tails/
Branch: obsolete_issue
Last Commit: 0bfc73bf0f468208a9bdbcf95467d792fe059332

Cheers.
xin