car docs: speedup test (#26337)

* faster

* faster

selfdrive/car/tests/test_docs.py

@@ -10,8 +10,9 @@ from selfdrive.car.honda.values import CAR as HONDA
 
 
 class TestCarDocs(unittest.TestCase):
-  def setUp(self):
-    self.all_cars = get_all_car_info()
+  @classmethod
+  def setUpClass(cls):
+    cls.all_cars = get_all_car_info()
 
   def test_generator(self):
     generated_cars_md = generate_cars_md(self.all_cars, CARS_MD_TEMPLATE)