Remove explicit batch network flag for TRT 10+ (#24298)
### Description
`nvinfer1::NetworkDefinitionCreationFlag::kEXPLICIT_BATCH` [has been
deprecated since
10.0](https://docs.nvidia.com/deeplearning/tensorrt/latest/_static/c-api/namespacenvinfer1.html#aa8f406be96c14b7dbea548cf19f09a08)
and is always implicitly set for versions 10.0+. Change the EP code to
only set this flag for TRT versions 8 and below.
### Motivation and Context
Removes deprecated API usages in the TRT EP code.
Signed-off-by: Kevin Chen <kevinch@nvidia.com>
