[facets] should remove groupby from base rqlst. Closes #1796196
as we search for values for a variable, there seems to be no case
where we would be interested in groups, though there are clearly
some were leaving groups cause errors.
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/web usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/share/cubicweb/cubes/shared/data usr/share/cubicweb/cubes/shared
debian/tmp/usr/share/cubicweb/cubes/shared/wdoc usr/share/cubicweb/cubes/shared