fix(ui5-calendar): fix header month button text localization

Fixes: #5242

Author: ilhan007

packages/main/src/Calendar.js

@@ -290,7 +290,7 @@ class Calendar extends CalendarPart {
 
 		const yearFormat = DateFormat.getDateInstance({ format: "y", calendarType: this.primaryCalendarType });
 		const localeData = getCachedLocaleDataInstance(getLocale());
-		this._headerMonthButtonText = localeData.getMonths("wide", this.primaryCalendarType)[this._calendarDate.getMonth()];
+		this._headerMonthButtonText = localeData.getMonthsStandAlone("wide", this.primaryCalendarType)[this._calendarDate.getMonth()];
 
 		if (this._currentPicker === "year") {
 			const rangeStart = new CalendarDate(this._calendarDate, this._primaryCalendarType);