Update to holiday_lv_lv
Grammar corrections for latvian holiday names in latvian.
Latvian language can be quite iffy, to say the least, where word endings differ based on context. Most of the changes are for the used ending of word "day".
In something like a name of a holiday, the generic ending is used, resulting in "diena". The previously used variation "dienu", is for a context where "day" is treated as an object and used(in a way) by someone.
"Mother's day" -> "Mātes diena" "They were celebrating Mother's day" -> "Viņi svinēja Mātes dienu" "I took a day off" -> "Es paņēmu brīvu dienu"