doc: Add comment about similar code.

src/components/DataExportSection.vue

@@ -168,6 +168,8 @@ export default class DataExportSection extends Vue {
    * @throws {Error} If export fails
    */
   public async exportDatabase(): Promise<void> {
+    // Note that similar code is in ContactsView.vue exportContactData()
+
     if (this.isExporting) {
       return; // Prevent multiple simultaneous exports
     }