webapp: Point main frontend to main db (belvedere)

As a temporary solution for somerset running out of disk space.

Related to T2562

Test Plan

octocatalog-diff:

.../puppet-environment $ bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details --to staging moma
Found host moma.softwareheritage.org
Cloning into '/tmp/swh-ocd.wkxiuUdR/environments/production/data/private'...
done.
Cloning into '/tmp/swh-ocd.wkxiuUdR/environments/staging/data/private'...
done.
*** Running octocatalog-diff on host moma.softwareheritage.org
I, [2020-09-04T08:55:50.643782 #16833]  INFO -- : Catalogs compiled for moma.softwareheritage.org
I, [2020-09-04T08:55:52.138109 #16833]  INFO -- : Diffs computed for moma.softwareheritage.org
diff origin/production/moma.softwareheritage.org current/moma.softwareheritage.org
*******************************************
  File[/etc/softwareheritage/storage/storage.yml] =>
   parameters =>
     content =>
      @@ -3,5 +3,5 @@
         cls: local
         args:
      -    db: host=somerset.internal.softwareheritage.org port=5432 user=swhstorage dbname=softwareheritage
      +    db: host=db.internal.softwareheritage.org port=5432 user=swhstorage dbname=softwareheritage
             password=swh::deploy::storage::db::password
           objstorage:
*******************************************
*** End octocatalog-diff on moma.softwareheritage.org

---

Migrated from D3879 (view on Phabricator)