LPS-51290 BaseAssetSearchTestCase's poor expiration date generation mayb...

...e too close to current time causing JournalArticle validation to fail

Fix for https://test-14-2.liferay.com/job/test-portal-pullrequest-backend%28master%29/325/group=22,label_exp=!test-14-2/testReport/junit/com.liferay.portlet.journal.asset/JournalArticleAssetSearchTest/testOrderByExpirationDateAsc/