[FIX] hr_holidays: don't use "object shorthand" (es6)

This commit fix non-compliant JS code syntax.

Currently Odoo JavaScript code base supports ECMAScript <= 5 only

Using ECMAScript 6 (2015) feature break compatibility with
Internet Explorer and Android KitKat (4.4)

Ref: https://eslint.org/docs/rules/object-shorthand

closes odoo/odoo#33605

Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/hr_holidays/static/src/js/leave_stats_widget.js

@@ -60,7 +60,7 @@ odoo.define('hr_holidays.LeaveStatsWidget', function (require) {
          * @param {Object} state
          * @returns {String[]} list of updated fields
          */
-        _setState(state) {
+        _setState: function (state) {
             var updatedFields = [];
             if (state.data.employee_id.res_id !== (this.employee && this.employee.res_id)) {
                 updatedFields.push('employee');