Use the C.UTF-8 locale

The glibc 2.35-6 package ships with the C.UTF-8 locale included.
This means there is now a UTF-8 locale available by default and en_US.UTF-8, which requires editing /etc/locale.gen and running locale-gen, is not needed anymore.
8 jobs for C.UTF-8 in 16 minutes and 26 seconds (queued for 1 second)