Update Uvicorn to 0.3.3 (#4024)

frameworks/Python/uvicorn/requirements.txt

@@ -1,5 +1,5 @@
 asyncpg==0.16.0
 jinja2==2.10
 ujson==1.35
-uvicorn==0.2.7
+uvicorn==0.3.3
 gunicorn==19.9.0