Revert "Address middleware compatibility issue on FastAPI"

This reverts commit 3b4019c.

Author: vishalbollu

pkg/workloads/cortex/serve/serve.py

@@ -25,13 +25,11 @@
 
 from fastapi import Body, FastAPI
 from fastapi.exceptions import RequestValidationError
+from fastapi.middleware.cors import CORSMiddleware
 from starlette.requests import Request
 from starlette.responses import Response
 from starlette.background import BackgroundTasks
 from starlette.exceptions import HTTPException as StarletteHTTPException
-from starlette.applications import Starlette
-from starlette.middleware import Middleware
-from starlette.middleware.cors import CORSMiddleware
 
 from cortex import consts
 from cortex.lib import util
@@ -57,17 +55,15 @@
     ThreadPoolExecutor(max_workers=int(os.environ["CORTEX_THREADS_PER_WORKER"]))
 )
 
-middleware = [
-    Middleware(
-        CORSMiddleware,
-        allow_origins=["*"],
-        allow_credentials=True,
-        allow_methods=["*"],
-        allow_headers=["*"],
-    )
-]
-
-app = FastAPI(middleware=middleware)
+app = FastAPI()
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
 
 local_cache = {"api": None, "predictor_impl": None, "client": None, "class_set": set()}