tests: re-add module argument

These were removed as part of dead code removal, but they are actually
needed in the integration tests for comparing with the configuration
generated by the installation.

tests/integration/standalone/alice-home-init.nix

@@ -1,3 +1,5 @@
+{ config, pkgs, ... }:
+
 {
   # Home Manager needs a bit of information about you and the paths it should
   # manage.

tests/integration/standalone/home-with-symbols-init.nix

@@ -1,3 +1,5 @@
+{ config, pkgs, ... }:
+
 {
   # Home Manager needs a bit of information about you and the paths it should
   # manage.

treefmt.toml

@@ -9,6 +9,10 @@ includes = [ "*.nix" ]
 command = "deadnix"
 options = [ "--edit", "--no-lambda-arg" ]
 includes = [ "*.nix" ]
+excludes = [
+  "tests/integration/standalone/alice-home-init.nix",
+  "tests/integration/standalone/home-with-symbols-init.nix"
+]
 
 [formatter.keep-sorted]
 command = "keep-sorted"