Remove invidious.f5.si due to instabilities

Removed invidious.f5.si from the list of public instances.

Author: unixfox

docs/instances.md

@@ -12,7 +12,6 @@
 
 * [inv.nadeko.net](https://inv.nadeko.net) 🇨🇱 - Source code/changes: https://git.nadeko.net/Fijxu/invidious - CAPTCHA: Go-away
 * [yewtu.be](https://yewtu.be) 🇩🇪 - Source code/changes: https://github.com/yewtudotbe/invidious-custom
-* [invidious.f5.si](https://invidious.f5.si) 🇯🇵 - Cloudflare
 * [invidious.nerdvpn.de](https://invidious.nerdvpn.de) 🇺🇦 - Source code/changes: https://git.nerdvpn.de/NerdVPN.de/invidious
 
 ### Tor Onion Services: