[session] drop session-as-a-context-manager
It made little sense in the 3.19 - session-as-cnx-bw-compat era, maybe.
Related to #1381328.
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/html/index.html
Files: /usr/share/doc/cubicweb-documentation/html/*