[editor] Fix TextEditor syntax

Mistake while merging earlier.

projects/editor/src/app/components/unit-view/page-view/rich-text-editor.component.ts

@@ -42,7 +42,6 @@ export class RichTextEditorComponent implements AfterViewInit {
       }),
       Heading.configure({
         levels: [1, 2, 3, 4]
-      })
       }),
       fontSizeExtension
     ]