Add NVTX purple color

[victoroliv2]

What does this PR do?

Fixing build error in cpp/runtime/qwen3OmniTTSRuntime.cpp

Usage

Build fails with ENABLE_NVTX_PROFILING=ON

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⚙️ Compatibility

• The change is backward compatible

Additional Information

[nvluxiaoz]

Thanks! We are aware of this, and this will be included in the next release.

[nvluxiaoz]

This MR should be included by https://github.com/NVIDIA/TensorRT-Edge-LLM/tree/release/0.7.0. Closing. Please reopen if the issue is not resolved. Thanks a lot for your contribution!