Fix issues in network after updating httpx to 0.21.x (#3169)

* [mod] upgrade httpx 0.21.2

httpx 0.21.2 and httpcore 0.14.4 fix multiple issues:
* https://github.com/encode/httpx/releases/tag/0.21.2
* https://github.com/encode/httpcore/releases/tag/0.14.4



so most of the workarounds in searx.network have been removed.

* pick even more changes from searxng

Co-authored-by: Alexandre Flament <alex@al-f.net>