feat: reduce block sizes and add tearDownClass for cleanup in LTX2 smoke test

Author: Perseus14

src/maxdiffusion/tests/generate_ltx2_smoke_test.py

@@ -97,6 +97,13 @@ def test_ltx2_inference(self):
       print(f"Audio produced with shape: {audios[0].shape}")
       self.assertGreater(len(audios), 0)
 
+  @classmethod
+  def tearDownClass(cls):
+    del cls.pipeline
+    import gc
+    
+    gc.collect()
+
 
 if __name__ == "__main__":
   unittest.main()