testresults.qt.io need to have active python version

Currently due to centos 7 run on testresults, the installed Python version is 3.6. This version came to the end of life in 2011 and gets no security updates. It also affects some of my python scripts since they use very old versions of python packages.
We should upgrade it to some newer version or at least one that supports security updates.

https://devguide.python.org/versions/