[FIX] sap.ui.commons.SearchField: Fix Screenreader Announcement

Change-Id: Id35796c32a27882223dbeec71b0e76c033d36bda
BCP: 1472015221
CR-Id: 012006153200015631792014
Merge "[FIX] sap.ui.commons.SearchField: Fix Screenreader Announcement" into rel-1.26