Downgrade webdriverio v9 to v8

[moiikana]

We upgraded webdriverio from v8 to v9 here: #806

• this has lead to dependency clashes (dependencies not resolvable during npm install)

[gbirke]

I'd rather have us fix the packages to keep the new major version, because the root cause of the incompatibility is an improvement in version 8.5 how webdriverio downloads browsers, see https://webdriver.io/blog/2023/07/31/driver-management/
Version 9 removes the dependency on the services, see https://webdriver.io/blog/2024/08/15/webdriverio-v9-release#removal-of-devtools-and-wdiodevtools-service-packages

I'm not sure what steps need to be done, I just had a glance at the docs after some googling and watching half of https://www.youtube.com/watch?v=3jMX4NYPPVk

removing the wdio-chromedriver-service made npm update/npm install work again, but I haven't tested if the screenshotting still works