Bug 18915: (QA follow-up) Add note for installs after 17.05

Bug 18915: (QA follow-up) Add note for installs after 17.05

Since the 17.05 upgrade adds the note and the sql file did not yet include
the note, we should add it when it is not there (for example new 17.11s).

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Tested by running the dbrev while there is a letter and while not.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>