test: dont install onnx

Author: jlwalke2

tox.ini

@@ -52,7 +52,7 @@ deps =
     tests: nbconvert
     tests: nbformat
     tests: torch
-    tests: onnx
+#    tests: onnx
 #    tests: h2o
 #    tests: tensorflow
 #    tests: lightgbm ; platform_system != "Darwin"  # lightgmb seems to have build issues on MacOS