.gitignore: Remove ARCH

The file was dropped in c7c7b36

Author: cfergeau

packaging/.gitignore

@@ -5,7 +5,6 @@ root/
 /darwin/Resources/welcome.html
 /darwin/scripts/postinstall
 /VERSION
-/ARCH
 /windows/msi/
 /windows/product.wxs
 vfkit.entitlements