port to libsoup3

https://salsa.debian.org/mpd-team/gmpc/-/blob/debian/latest/debian/patches/download-port-from-libsoup2.4-to-libsoup3.patch
Index: configure.ac
--- configure.ac.orig
+++ configure.ac
@@ -231,7 +231,7 @@ AC_SUBST(gthread_LIBS)
 AC_SUBST(gthread_CFLAGS)
 
 #libsoup
-PKG_CHECK_MODULES([libsoup], libsoup-2.4)
+PKG_CHECK_MODULES([libsoup], libsoup-3.0)
 AC_SUBST(libsoup_LIBS)
 AC_SUBST(libsoup_CFLAGS)
 
