Update butler URL to fix getbutler.sh (#189)

The recommended URL has changed as per the documentation:

https://itch.io/docs/butler/installing.html#the-automation-friendly-way

Co-authored-by: Perjéssy Lóránt <lostlont@users.noreply.github.com>

getbutler.sh

@@ -3,7 +3,7 @@
 mkdir -p /opt/butler/bin 
 cd /opt/butler/bin
 
-wget -O butler.zip https://broth.itch.ovh/butler/linux-amd64/LATEST/archive/default
+wget -O butler.zip https://broth.itch.zone/butler/linux-amd64/LATEST/archive/default
 unzip butler.zip
 
 # GNU unzip tends to not set the executable bit even though it's set in the .zip