build: fix Windows installer

The Hungarian language file for the Windows installer was recently moved
from unofficial to the officially supported languages. However, a new
release including Hungarian by default is not available yet. This causes
our CI to fail because it can't find Hungarian in unofficial.

We change our ci script to download Hungarian from the correct location
for official languages, and adapt gimp3264.iss to reflect the correct
location.
15 jobs for !715 with wip/wormnest/fix-installer in 42 minutes and 26 seconds (queued for 1 second)
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