Migrate docs from Sphinx to MkDocs (#18145)

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

vllm/executor/ray_distributed_executor.py

@@ -528,12 +528,12 @@ class RayDistributedExecutor(DistributedExecutorBase):
         ray.get(parallel_worker_tasks)
 
     def _check_ray_cgraph_installation(self):
-        import pkg_resources
+        import importlib.metadata
+
         from packaging import version
 
         required_version = version.parse("2.43.0")
-        current_version = version.parse(
-            pkg_resources.get_distribution("ray").version)
+        current_version = version.parse(importlib.metadata.version("ray"))
         if current_version < required_version:
             raise ValueError(f"Ray version {required_version} is "
                              f"required, but found {current_version}")