Update to webkit2gtk-4.1 (4.0 is removed from new releases of linux)

[lvlrt]

Library already supports 4.1, but the go-code requires 4.0 to be installed - but 4.0 is now not available anymore in many new installations of Linux (Ubuntu 24.04)

[phildremi]

Thanks for the PR! I don't think this repository is currently maintained, but I'll leave some info here regardless:

• The ubuntu-latest tag does refer to ubuntu-24.04 now (see runner-images/README and blog post)
• CI runs already use webkit2gtk-4.1, except for one configuration which may need updating (?)
• Workflows are pinned to ubuntu-22.04, where several package versions are still available
• Upgrading the runner image is likely to break other things - compare docs for 22.04 vs. 24.04

(I don't have permissions to approve or merge changes and I don't know Go anyway.)