libsoup: Bump to 2.74 to fix gssapi build failure on macOS
See: https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/255
We also need to disable sysprof by default because it only builds on
native Linux. If someone really wants it, they can enable the option
on the command-line by passing -Dlibsoup:sysprof=enabled