fix(typeahead): use inline style for live element

Use inline style instead of the bootstrap class for the live element
to support the usage of the component in the shadow DOM.
Fixes ng-bootstrap#4560

src/util/accessibility/live.ts

@@ -16,7 +16,16 @@ function getLiveElement(document: any, lazyCreate = false): HTMLElement | null {
 		element.setAttribute('aria-live', 'polite');
 		element.setAttribute('aria-atomic', 'true');
 
-		element.classList.add('visually-hidden');
+		// Visually hide the element
+		element.style.position = 'absolute';
+		element.style.width = '1px';
+		element.style.height = '1px';
+		element.style.padding = '0';
+		element.style.margin = '-1px';
+		element.style.overflow = 'hidden';
+		element.style.clipPath = 'inset(100%)';
+		element.style.whiteSpace = 'nowrap';
+		element.style.border = '0';
 
 		document.body.appendChild(element);
 	}