docs: install with pacman -Syu so the repo setup does not fail on a partial upgrade (#23)

Co-authored-by: Tri Vo Khac <git@trivk.dev>

README.md

@@ -46,7 +46,7 @@ Server = https://git.trivk.dev/api/packages/tri/arch/$repo/$arch
 ```
 
 ```sh
-sudo pacman -Sy qtpotato
+sudo pacman -Syu qtpotato
 ```
 
 The package is built against Arch's current Qt and KDE Frameworks. If it breaks after a system