www/firefox-esr-i18n: fix available language packs

Kashubian and Kurdish and are no longer available

https://bugzilla.mozilla.org/show_bug.cgi?id=1104047
https://bugzilla.mozilla.org/show_bug.cgi?id=1104033

See also: https://l10n.mozilla.org/teams/
MFH: 2015Q3
X-MFH-With: r392273