docs: remove function call from all backend feature installation instructions

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/features/software-templates/writing-templates.md

@@ -891,7 +891,7 @@ const scaffolderModuleCustomFilters = createBackendModule({
 const backend = createBackend();
 backend.add(import('@backstage/plugin-scaffolder-backend/alpha'));
 /* highlight-add-next-line */
-backend.add(scaffolderModuleCustomFilters());
+backend.add(scaffolderModuleCustomFilters);
 ```
 
 If you still use the legacy backend system, then you will use the `createRouter()` function of the `Scaffolder plugin`

docs/features/techdocs/how-to-guides.md

@@ -800,7 +800,7 @@ const techdocsCustomBuildStrategy = createBackendModule({
 
 /* highlight-add-start */
 backend.add(import('@backstage/plugin-techdocs-backend/alpha'));
-backend.add(techdocsCustomBuildStrategy());
+backend.add(techdocsCustomBuildStrategy);
 /* highlight-add-end */
 
 backend.start();