[VitisAI] update graph_save (#20979)
### Description
<!-- Describe your changes. -->
Fix the threshold limit
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
We use this to debug the graph after each graph transformation. But, the
const data inside the model is useless.
So, we decided to remove that information to save disk space.
Co-authored-by: Chunye Wang <chunywan@xlnx.xilinx.com>
