fix: arrow up/down highlighting moves off list

When using keyboard arrow up/down to highlight items where there are
more suggestions than can be displayed by the maxResults parameter,
the highlight disappears but is still selecting an item, allowing
selection of a non-visible suggestion.

This limits keyboard highlighting to the lesser of the number of
suggestions or the value of maxResults.

src/auto-complete/auto-complete.component.ts

@@ -565,7 +565,7 @@ export class AutoCompleteComponent implements AfterViewChecked, ControlValueAcce
       this.showItemList();
     }
 
-    const max = this.suggestions.length - 1;
+    const max = this.suggestions.length > this.maxResults ? this.maxResults - 1 : this.suggestions.length - 1;
 
     if (direction < 0) {
       if (this.focusedOption === -1 || this.focusedOption === max) {