Deploy add-forge-now functionality in production

Related to T4329

Test Plan

octo-diff on moma, it activates the functionality:

$SWH_PUPPET_ENVIRONMENT_HOME/bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details --to staging moma
Found host moma.softwareheritage.org
...
diff origin/production/moma.softwareheritage.org current/moma.softwareheritage.org
*******************************************
  File[/etc/softwareheritage/web/web.yml] =>
   parameters =>
     content =>
      @@ -97,5 +97,5 @@
         email_address: add-forge-now@archive.softwareheritage.org
       features:
      -  add_forge_now: false
      +  add_forge_now: true
       allowed_hosts:
       - archive.softwareheritage.org
*******************************************
*** End octocatalog-diff on moma.softwareheritage.org

---

Migrated from D7983 (view on Phabricator)