cubicweb #4763360 [web] everything old is new again [validation pending]

[web] everything old is new again

Kill the "new" cubicweb.css, and move cubicweb.old.css back in its place.

prioritynormal
typebug
done in3.20.0
load1.000
load left0.000
closed by#23af005426bf [web] everything old is new again
patch[web] everything old is new again [applied]