Update onnxruntime version to 1.18.1 for compatibility with onnx 1.16

Author: chrisdengso

requirements.txt

@@ -15,7 +15,10 @@ numpy<2
 opencv-python
 scikit-image
 onnx==1.16.0
-onnxruntime==1.16.3
+# 1.18.1 is the release paired with onnx 1.16; also the first pin whose wheels
+# drop the executable-stack (GNU_STACK RWX) flag that newer kernels refuse,
+# which crashed onnxruntime import in-cluster.
+onnxruntime==1.18.1
 PyTurboJPEG==1.7.5
 exifread
 tritonclient[http,grpc]