fix: just increase the minor version number since it doesn't change API

Author: shilei-massclouds

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "scheduler"
-version = "0.3.0"
+version = "0.2.1"
 edition = "2021"
 authors = ["Yuekai Jia <equation618@gmail.com>"]
 description = "Various scheduler algorithms in a unified interface"