refactor(DateUtils.test.js): use matcher toBe() instead of toEqual()

Quote from https://jestjs.io/docs/using-matchers:

> toBe uses Object.is to test exact equality. If you want to check the value of an object, use toEqual instead

Author: php-coder

src/main/frontend/src/utils/DateUtils.test.js

@@ -4,7 +4,7 @@ describe('DateUtils.formatDateToDdMmYyyy()', () => {
 
 	it('should return a string in a format dd.mm.yyyy', () => {
 		const date = new Date('2018-06-12T16:59:54.451Z');
-		expect(DateUtils.formatDateToDdMmYyyy(date)).toEqual('12.06.2018');
+		expect(DateUtils.formatDateToDdMmYyyy(date)).toBe('12.06.2018');
 	});
 
 });