i18n: update el.js (#9831)
i18n: update el.js (#9831)

Hello from Greece to element-ui community. Just change confirm from "ok" to "Εντάξει". More correct Greek word for "ok". Also attempts for
* PrevYear, 
* nextYear, 
* prevMonth, 
* nextMonth. 
*deleteTip,
sumText,
Titles-Lists,
filterPlaceholder,
noCheckedFormat,
Just direct translation, not tested on components yet. Any comment or recommendation accepted.....
by the way, keep up the good work, and im lover of dark themes............
Raganof/element,Raganof/element,ElemeFE/element,baiyaaaaa/element,baiyaaaaa/element,huguangju/element,Kingwl/element,ElemeFE/element,Kingwl/element,huguangju/element