Summary:
* Model was problematic.
* Fixes landed to 1.3.3 and model imported fine.
* User discovered trouble still existing (model output not the right dimension?) 
* User upgraded to 1.4.0 but model does not import anymore.

--> Regression, however once model import again we need to check about the dimension trouble to be sure to fully fix this (more detail on github issue).

Long story:

from [https://github.com/Unity-Technologies/barracuda-release/issues/169]

itself a follow up of [https://github.com/Unity-Technologies/barracuda-release/issues/156] 

On 1.4.0 Model fail to import because of Pad operator using constant path for `pads` attribute:

!image-2021-04-29-15-46-14-317.png!