removing dateform parameter from getMonthShortInLocale that was never sent and was taking the value of the locale variable, creating a bug when setting a locale with the month/year picker (#1702)

Author: athomaj

src/date_utils.js

@@ -295,7 +295,7 @@ export function getMonthInLocale(month, locale) {
   return formatDate(setMonth(newDate(), month), "LLLL", locale);
 }
 
-export function getMonthShortInLocale(month, dateFormat, locale) {
+export function getMonthShortInLocale(month, locale) {
   return formatDate(setMonth(newDate(), month), "LLL", locale);
 }