gjs.tests: fix warning

The tests complained:

/nix/store/nm3nf5y4hzgmy00lw5s6ls68j38y84y0-gjs-1.72.0-installedTests/libexec/installed-tests/gjs/scripts/testCommandLineModules.sh: line 90: gjs-console: command not found

But they still passed.

Changed files
+6
nixos
tests
installed-tests
+6
nixos/tests/installed-tests/gjs.nix
···
makeInstalledTest {
tested = pkgs.gjs;
withX11 = true;
+
+
testConfig = {
+
environment.systemPackages = [
+
pkgs.gjs
+
];
+
};
}