Bug#1070405: darktable: Please drop unused Build-Depends: libsoup2.4-dev

[Jeremy Bícha]

Source: darktable
Version: 4.6.1-2

Please drop Build-Depends: libsoup2.4-dev . It isn't used at all and
we would eventually like to remove libsoup2.4 from Debian.

Thank you,
Jeremy Bícha