Bug 42301: Fix error occuring on updatedatabase when using MySQL

This patch fixes an error when running updatedatabase on an instance using MySQL by defining a key length for an unique key. The unique key in table record_sources was introduced on 35380 but was lacking a key length which works in mariaDB but fails on MySQL.

Test plan:
a) run ktd with mysql f.e.: DB_IMAGE=mysql:8.0 ktd --proxy --name mysql8 up -d
b) enter ktd shell ktd --name mysql8 --shell
c) checkout a Koha version prior to 35380. f.e. "git checkout 67adbce6562fa352b143977747fa290f23c63fde"
d) run 'reset_all'
e) log in and check Koha version in http://mysql8-intra.localhost/cgi-bin/koha/about.pl which should show
25.12.00.036
f) git checkout main
g) restart_all
h) updatedatabase will throw the following error:
Upgrade to 25.12.00.037  [08:29:14]: Bug 35380 - Add new unique name to record sources, add default record sources, add is_system column to default record sources.
        ERROR: {UNKNOWN}: DBI Exception: DBD::mysql::db do failed: BLOB/TEXT column 'name' used in key specification without a key length at /kohadevbox/koha/C4/Installer.pm line 817
i) apply patch
j) 'updatedatabase' should run without errors now

Signed-off-by: Martin Renvoize <martin.renvoize@openfifth.co.uk>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>

installer/data/mysql/db_revs/251200037.pl

@@ -13,7 +13,7 @@ return {
             $dbh->do(
                 q{
                 ALTER TABLE record_sources
-                ADD UNIQUE KEY name (`name`)
+                ADD UNIQUE KEY name (`name`(191))
             }
             );
             say $out "Added unique key 'name' ";