fix(ui5-multi-combobox): Prevent scrolling on page up/down (#4835)

* Prevent scrolling on page up/down in the Multi Combobox

* Remove redundant imports

packages/main/src/MultiComboBox.js

@@ -585,6 +585,14 @@ class MultiComboBox extends UI5Element {
 		this[`_handle${event.key}`] && this[`_handle${event.key}`](event);
 	}
 
+	_handlePageUp(event) {
+		event.preventDefault();
+	}
+
+	_handlePageDown(event) {
+		event.preventDefault();
+	}
+
 	_handleBackspace(event) {
 		if (event.target.value === "") {
 			event.preventDefault();