niri: preserve string context in generated config

lib.trim goes through builtins.match, which discards string context, so
store paths in wayland.windowManager.niri.settings end up as inert text in
niri/config.kdl with nothing rooting the referenced packages.

toKDL only ever appends a single trailing newline, so lib.removeSuffix
strips it just as well and keeps the context.

Author: znaniye

modules/services/window-managers/niri.nix

@@ -188,7 +188,7 @@ in
           escapeBackslashes = true;
           escapeTabs = true;
         };
-        settings = lib.trim (toKDL cfg.settings);
+        settings = lib.removeSuffix "\n" (toKDL cfg.settings);
         configLines = lib.concatStringsSep "\n" (
           lib.filter (line: line != "") [
             cfg.extraConfigEarly