[TRI-978][fix] Bump tensorrt_llm submodule to fix streaming/metrics CI failures (main)

[mc-nv]

Summary

Bumps the tensorrt_llm submodule to 2fdb9e6 to bring in TRI-978 fixes:

• streaming=None coercion in model.py (executor crash fix)
• DST timezone fix in convertTimestampToMicroseconds (tm_isdst=-1)
• Explicit streaming tensor in benchmark_core_model.py
• Switch benchmark to gRPC to avoid gevent segfault on aarch64
• Test assertion and timestamp fixes in custom_metrics_verification_tests.py

^{Relates-to: TRI-978 | Sister PR for r26.04: #855}