tests: use master commit for pytest on 3.10 (#2967)

Author: henryiii

tests/requirements.txt

@@ -5,7 +5,8 @@ numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux")
 numpy==1.20.0; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
-pytest==6.2.1; python_version>="3.6"
+pytest==6.2.1; python_version>="3.6" and python_version<="3.9"
+pytest @ git+https://github.com/pytest-dev/pytest@c117bc350ec1e570672fda3b2ad234fd52e72b53; python_version>="3.10"
 pytest-timeout
 scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"
 scipy==1.5.4; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"