Fix improper iterator usage (#24698)
### Description
<!-- Describe your changes. -->
This pull request includes a minor but important fix to the iteration
logic in the `NvExecutionProvider::GetCapability` method to ensure
correctness and avoid potential undefined behavior when removing
elements from a container during iteration.
### Iteration logic fix:
* In
`onnxruntime/core/providers/nv_tensorrt_rtx/nv_execution_provider.cc`,
the loop for removing subgraphs smaller than the minimal size was
updated to use `it = supported_nodes_vector.erase(it)` instead of
`erase(it--)`. This ensures the iterator remains valid and avoids
decrementing it unnecessarily, improving code safety and readability.
### Motivation and Context
Prevent possible memory corruption.
Similar code was addressed in tensorrt EP.
