Use `--upgrade` option to upgrade pip with pip in workflow, instead
of non-existing `-u` option (-U would also be possible).
Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>
1. update action/setup-python to latest version
2. pin major version to be used to 3.x
3. upgrade pip before using it
1 and 2 were suggested in #2089
Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>
