build: Re-enable youtube plugin with soup3-enabled libgdata
libgdata got ported to libsoup3 and got its identifier changed from libgdata to libgdata-1.0. There are no visible API changes in this new version.
libgdata got ported to libsoup3 and got its identifier changed from libgdata to libgdata-1.0. There are no visible API changes in this new version.