Tests: Fix t_json_only_debugcheck to not need sensitive golden file

test_regress/t/t_json_only_debugcheck.py

@@ -7,6 +7,7 @@
 # SPDX-FileCopyrightText: 2024 Wilson Snyder
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
+import json
 import vltest_bootstrap
 
 test.scenarios('vlt')
@@ -21,6 +22,11 @@ test.compile(verilator_flags2=[
              make_top_shell=False,
              make_main=False)
 
-test.files_identical(out_filename, test.golden_filename, 'logfile')
+# not files_identical as output is too sensitive to internal changes
+test.file_grep(out_filename, r'"type":"MODULE"')
+
+# check JSON is parsable
+with open(out_filename, 'r', encoding="utf8") as fh:
+    json.load(fh)
 
 test.passes()