Use consistent format

debian/preinst

@@ -55,7 +55,7 @@ case "$1" in
     fi
 
     # Clean up old Emby cruft that can break the user's system
-    test -f /etc/sudoers.d/emby && rm -f /etc/sudoers.d/emby
+    [[ -f /etc/sudoers.d/emby ]] && rm -f /etc/sudoers.d/emby
 
     ;;
   abort-upgrade)