appimage: remove node_modules from appdir

The node modules do not need to be deliverer with the appimage. Removing
them from the AppDir saves 50MB.

appimage/build_appimage.sh

@@ -186,6 +186,14 @@ build_frontend() {
   log_message "Generating front end"
   npm run dist
   popd || handle_error
+
+  remove_node_modules
+}
+
+remove_node_modules() {
+  # Node has served its purpose. We don't need to deliver the node modules with
+  # the AppImage.
+  rm -rf "$ISLAND_PATH"/cc/ui/node_modules
 }
 
 add_monkey_icon() {