OneDNN/dnnl: Fix filepath after dnnl move (#20086)
### Description
This adjusts the path used in the nuget script for dnnl to the new
location of the file.
There isn't a CI pipeline for this as far as I can tell, and I can't
easily confirm this change works on master, so please check.
### Motivation and Context
It is currently not possible to build onednn nuget packages. It's
possible that the correct action would be to move the file not fix this
path, but I'm not familiar enough with the repository layout.
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Co-authored-by: Tianlei Wu <tlwu@microsoft.com>
