Fix localisation error in DB upgrade script

The upgrade script for 4.3.6 has a hard-coded lookup for the 'Credit
Card' payment_instrument, but uses the (default) `label` column for the
lookup, which is localised -- i.e. the upgrade fails fatally on any
setup where the 'Credit Card' label is translated.

Fix by using the non-localised `name` column instead.
Merge pull request #1413 from sfe-ev/4.3.6-upgrade_fix

Fix localisation error in DB upgrade script