stack/lamp: remove stunnel as it's not used

Also move component/stunnel to unstable

stack/lamp/buildout.cfg

@@ -23,7 +23,6 @@ extends =
   ../../component/mariadb/buildout.cfg
   ../../component/perl/buildout.cfg
   ../../component/sqlite3/buildout.cfg
-  ../../component/stunnel/buildout.cfg
   ../../component/xz-utils/buildout.cfg
   ../../component/zlib/buildout.cfg
   ../erp5/buildout.cfg
@@ -83,7 +82,6 @@ context =
     key logrotate_cfg template-logrotate-base:rendered
     key gzip_location gzip:location
     key xz_utils_location xz-utils:location
-    key stunnel_location stunnel:location
     key template_monitor monitor2-template:rendered
     key mariadb_link_binary template-mariadb:link-binary
     key mariadb_location mariadb:location