onnxruntime

Update Win_GPU_CI trigger (#13290)

### Description
supplement of #13248

Add PR trigger 

https://learn.microsoft.com/en-us/azure/devops/pipelines/repos/github?view=azure-devops&tabs=yaml#pr-triggers

fix: master -> main

Testted with #13289 #13292

NB:
the real pipeline is always triggered if the workflow yaml changed even
it's added in the path filter.

### 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. -->
Make sure the real pipeline not run in the backend.