Replace lists with one item by the item, not before last currency has been
added. In this traceback 'MXN' is added to 'pesos' while pesos is no longer a
list as the optimization was carried out too early.
$ ./local/py3/bin/python searxng_extra/update/update_currencies.py
Traceback (most recent call last):
File "searxng_extra/update/update_currencies.py", line 164, in <module>
main()
File "searxng_extra/update/update_currencies.py", line 157, in main
add_currency_name(db, "pesos", 'MXN')
File "searxng_extra/update/update_currencies.py", line 89, in add_currency_name
iso4217_set.insert(0, iso4217)
AttributeError: 'str' object has no attribute 'insert'
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>