Remove annoying beep from content assist when no proposals found

The system beep fired every time content assist was manually invoked
but had no proposals to show, which is disruptive and unhelpful.

Author: vogella

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/CompletionProposalPopup.java

@@ -550,12 +550,6 @@ public String showProposals(final boolean autoActivated) {
 	 */
 	boolean hideWhenNoProposals(boolean autoActivated) {
 		if (autoActivated || !fContentAssistant.isShowEmptyList()) {
-			if (!autoActivated) {
-				Control control= fContentAssistSubjectControlAdapter.getControl();
-				if (control != null && !control.isDisposed()) {
-					control.getDisplay().beep();
-				}
-			}
 			hide();
 			return true;
 		}