fix API report

Signed-off-by: aramissennyeydd <aramis.sennyey@doordash.com>

packages/backend-plugin-api/report.api.md

@@ -251,6 +251,7 @@ export namespace coreServices {
       'root',
       'singleton'
     >;
+  const systemMetadata: ServiceRef<SystemMetadataService, 'root', 'singleton'>;
 }
 
 // @public

packages/backend-plugin-api/src/services/definitions/coreServices.ts

@@ -292,7 +292,7 @@ export namespace coreServices {
   
   /**
    * Read information about your current Backstage deployment.
-   * @alpha
+   * @public
    */
   export const systemMetadata = createServiceRef<
     import('./SystemMetadataService').SystemMetadataService