Update uproot4
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Beginning with 2nd June, only the "Single Sign On" option for login to the GitLab web interface will be possible. If you don't have an MPCDF wide second factor so far, please get one at our SelfService (https://selfservice.mpcdf.mpg.de). The GitLab internal second factor will not work.
Update code to use uproot v4. Uproot 3 has been deprecated (see https://github.com/scikit-hep/uproot3)