Turn @config into a dataclass_transform (#31541)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

vllm/config/observability.py

@@ -6,7 +6,6 @@ from typing import Any, Literal, cast
 
 from packaging.version import parse
 from pydantic import Field, field_validator, model_validator
-from pydantic.dataclasses import dataclass
 
 from vllm import version
 from vllm.config.utils import config
@@ -16,7 +15,6 @@ DetailedTraceModules = Literal["model", "worker", "all"]
 
 
 @config
-@dataclass
 class ObservabilityConfig:
     """Configuration for observability - metrics and tracing."""