Remove float64 numpy

ml-agents/mlagents/trainers/optimizer.py

 
     def _make_zero_mem(self, m_size: int, length: int) -> List[np.ndarray]:
         return [
-            np.zeros((m_size)) for i in range(0, length, self.policy.sequence_length)
+            np.zeros((m_size), dtype=np.float32)
+            for i in range(0, length, self.policy.sequence_length)
         ]