Fix a security warning in cuda gemm int8 kernel (#14335)
### Description
fix a security warning in GemmInt8 cuda kernel
### Motivation and Context
it is for issue:
https://dev.azure.com/aiinfra/ONNX%20Runtime/_workitems/edit/11158/
Co-authored-by: Cheng Tang <chenta@microsoft.com@orttrainingdev9.d32nl1ml4oruzj4qz3bqlggovf.px.internal.cloudapp.net>
