test: use _GROUPING_SPECS for JSON grouping tests too

Reuse the shared _GROUPING_SPECS list (with composite groupings) in
test_validate_grouping_json_cli, replacing the separate hardcoded list.

Co-Authored-By: Claude Code 2.1.81 / Claude Opus 4.6 <noreply@anthropic.com>

Author: yarikoptic

dandi/cli/tests/test_cmd_validate.py

@@ -484,16 +484,7 @@ def test_render_text_multilevel_grouping(capsys: pytest.CaptureFixture) -> None:
 @pytest.mark.ai_generated
 @pytest.mark.parametrize(
     "grouping",
-    [
-        ("path",),
-        ("severity",),
-        ("id",),
-        ("validator",),
-        ("standard",),
-        ("dandiset",),
-        ("severity", "id"),
-        ("validator", "severity"),
-    ],
+    [("path",), *_GROUPING_SPECS],
     ids=lambda g: "+".join(g),
 )
 def test_validate_grouping_json_cli(