Use cubicweb devel for docker image

Dockerfile

 ARG CW_INSTANCE_NAME=fresh
-FROM logilab/cubicweb:3.26-onbuild
+FROM logilab/cubicweb:dev-onbuild
 USER root
 RUN pip install -r /src/docker/requirements.txt
 RUN cp /src/docker/pyramid.ini.j2 /pyramid.ini.j2

cubicweb_fresh/__pkginfo__.py

@@ -20,7 +20,7 @@ classifiers = [
     ]
 
 __depends__ = {
-    'cubicweb[pyramid]': '>= 3.26.0, < 3.27',
+    'cubicweb[pyramid]': None,
     'cubicweb-expense': '>= 0.9.0',
     'cubicweb-workcase': '>= 0.8.0',
     'cubicweb-searchui': '>= 0.4.1',