Re-add "file" type for --add-location for xgettext call

Passing line numbers in the comments is bad.

References:

* Commit 94961b33
* Previous commit

util/updatepo.sh

@@ -50,7 +50,7 @@ cd ..
 potfile=po/minetest.pot
 xgettext --package-name=minetest \
 	--sort-by-file \
-	--add-location \
+	--add-location=file \
 	--keyword=N_ \
 	--keyword=wgettext \
 	--keyword=fgettext \