test_models: fix runaway memory growth for long running tests (#26295)

* delete can msgs

* only can msgs
old-commit-hash: d793d3622b

selfdrive/car/tests/test_models.py

@@ -109,6 +109,10 @@ class TestCarModelBase(unittest.TestCase):
     assert cls.CP
     assert cls.CP.carFingerprint == cls.car_model
 
+  @classmethod
+  def tearDownClass(cls):
+    del cls.can_msgs
+
   def setUp(self):
     self.CI = self.CarInterface(self.CP, self.CarController, self.CarState)
     assert self.CI