Drop more deprecated code This follows up on changeset a8c1ea390400, in which code deprecated using logilab.common.deprecation got dropped. Now we also drop code deprecated using stdlib's warn(<msg>, DeprecationWarning). Notice that, as a consequence of dropping old/new etypes aliases in cubicweb/schema.py, we drop the import ETYPE_NAME_MAP (no longer needed); but since other modules imported that name from cubicweb.schema, we need to update the import statement to use "cubicweb" directly.

Flake8 cubicweb/cwvreg.py

Drop deprecated "boxes" and "contentnavigation" registries