cubicweb-link #2894686 drop embed support [validation pending]

Current implementation use (and thus depends on) embed, which is deprecated (and has been extracted from cubicweb as of 3.17).

prioritynormal
typebug
done in1.7.0
load1.000
load left0.000
closed by#4a0c6101be41 drop embed support (closes #2894686)
patchwip drop embed support [applied]