Update dependency pytest-asyncio to v0.20.3

Author: renovate[bot]

requirements.txt

@@ -19,7 +19,7 @@ multidict==5.2.0; python_version >= "3.6"
 pycares==4.2.0
 pycparser==2.21; python_version >= "2.7" and python_full_version < "3.0.0" or python_full_version >= "3.4.0"
 pytest==6.2.5
-pytest-asyncio==0.17.2
+pytest-asyncio==0.20.3
 soupsieve==2.3.1; python_version >= "3.6" and python_full_version > "3.0.0"
 win32-setctime==1.0.4; sys_platform == "win32" and python_version >= "3.5"
 yarl==1.7.2; python_version >= "3.6"