Upgrade gunicorn (#2525)

Author: YuanTingHsieh

setup.cfg

@@ -23,7 +23,7 @@ install_requires =
     Flask-SQLAlchemy==3.1.1
     SQLAlchemy==2.0.16
     grpcio==1.62.1
-    gunicorn>=20.1.0
+    gunicorn>=22.0.0
     numpy
     protobuf==4.24.4
     psutil>=5.9.1