test: update the expectation for firefox CDP (#12047)

Author: OrKoN

test/TestExpectations.json

@@ -1390,6 +1390,13 @@
     "expectations": ["FAIL", "PASS"],
     "comment": "TODO: add a comment explaining why this expectation is required (include links to issues)"
   },
+  {
+    "testIdPattern": "[defaultbrowsercontext.spec] DefaultBrowserContext page.cookies() should work",
+    "platforms": ["darwin", "linux", "win32"],
+    "parameters": ["cdp", "firefox"],
+    "expectations": ["FAIL", "PASS"],
+    "comment": "Firefox CDP does not support isolation so this test might fail if other tests set cookies"
+  },
   {
     "testIdPattern": "[defaultbrowsercontext.spec] DefaultBrowserContext page.deleteCookie() should work",
     "platforms": ["darwin", "linux", "win32"],