hotfix: add type hints to scheduler mixins (#15916)

python/sglang/srt/managers/scheduler_profiler_mixin.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import logging
 import os
 import time

python/sglang/srt/multiplex/multiplexing_mixin.py

@@ -2,6 +2,8 @@
 Mixin class providing multiplexing scheduling logic
 """
 
+from __future__ import annotations
+
 import logging
 from typing import TYPE_CHECKING