Arm backend: Add mypy ignore for nss import

Signed-off-by: per.held@arm.com
Change-Id: I351b955621c8f5b807e4ead2722d3b7f0d98df51

Author: perheld

backends/arm/test/models/test_nss.py

@@ -19,7 +19,9 @@
 
 from huggingface_hub import hf_hub_download
 
-from ng_model_gym.usecases.nss.model.model_blocks import AutoEncoderV1
+from ng_model_gym.usecases.nss.model.model_blocks import (  # type: ignore[import-not-found,import-untyped]
+    AutoEncoderV1,
+)
 
 input_t = Tuple[torch.Tensor]  # Input x