Bug 1916582 - Fix firefox-ci new config test to avoid common variants. r=aryx, a=dsmith

Differential Revision: https://phabricator.services.mozilla.com/D221004

taskcluster/test/test_new_config.py

@@ -74,8 +74,9 @@ def test_tasks_new_config_false(full_task_graph, filter_tasks, func, min_expecte
                 t.kind == "test"
                 and t.attributes["unittest_suite"] == "mochitest-browser-chrome"
                 and t.attributes["test_platform"] == "linux1804-64-qr/opt"
+                and ("spi-nw" not in t.label and "a11y-checks" not in t.label)
             ),
-            64,
+            32,
             id="mochitest-browser-chrome",
         ),
     ),