build-sys: fix required libsoup version for webdav support
build-sys: fix required libsoup version for webdav support

guodong/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,flexVDI/spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,Fantu/spice-gtk,Fantu/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk