Bug 38274: Fix typo in arabic language description

Bug 38274: Fix typo in arabic language description

In installer/data/mysql/mandatory/subtag_registry.sql we see a missing
char in arabic language description.

Wee see this was correct before Bug 12250 :
العربية

Test plan :
1) Install a fresh Koha with this patch
2) Look in database :
   SELECT * FROM language_descriptions WHERE subtag='ar' AND type='language' AND lang='ar'
=> Check description is correct
3) On a old existing Koha
4) Install patch and run update database
=> Look in database and check description is correct

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>