Fix AUR link (oof that's embarassing, it's been like that for months)

README.md

@@ -112,7 +112,7 @@ go build -tags wayland .
 ## εγκατάσταση
 (installation)
 
-pi currently has no consolidated way of installing it. There is an [Arch User Repository package available](https://aur.archlinux.org/pi-im), which is maintained by [snit](https://isekai.rocks/~snit).
+pi currently has no consolidated way of installing it. There is an [Arch User Repository package available](https://aur.archlinux.org/packages/pi-im), which is maintained by [snit](https://isekai.rocks/~snit).
 
 ## υποστήριξη
 (support)