Enable mypy checking on V1 code (#11105)

Signed-off-by: Mark McLoughlin <markmc@redhat.com>

vllm/v1/worker/gpu_worker.py

@@ -204,7 +204,7 @@ class Worker:
         return output if self.rank == 0 else None
         return output
 
-    def profile(self, is_start=True):
+    def profile(self, is_start: bool = True):
         if self.profiler is None:
             raise RuntimeError("Profiler is not enabled.")
         if is_start: