Remove IE 11 workarounds and left-overs

[mfranzke]

https://blogs.windows.com/windowsexperience/2022/06/15/internet-explorer-11-has-retired-and-is-officially-out-of-support-what-you-need-to-know/

[mfranzke]

To be honest, I'm still struggling on aspects like e.g. still providing .woff fonts next to the .woff2, as this both wouldn't harm anything, but provide a working solution for any user (even if it might be a very low percentage) which are still bound to that browser (generation).

[mfranzke]

Internet Explorer 11 will be permanently disabled for certain versions of Windows 10 as part of the February 2023 Windows security update (“B”) release scheduled for February 14, 2023.

https://aka.ms/IEmodeFAQ