Upgrade Selenium version

[radeklawgmin]

Currently AET makes use of Selenium 3.141.
Upgrade it to version 4 or newer once some stable version is provided.

[malaskowski]

AFAIK, AET uses Selenium 3.8:
https://github.com/wttech/aet/blob/master/osgi-dependencies/selenium/pom.xml#L37

3.141 is the latest 3.X (major) version.