frontend-app-api: Update package discovery type name

Co-authored-by: Patrik Oldsberg <poldsberg@gmail.com>
Co-authored-by: Philipp Hugenroth <philipph@spotify.com>
Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Signed-off-by: Johan Haals <johan.haals@gmail.com>

packages/frontend-app-api/src/wiring/discovery.ts

@@ -35,7 +35,7 @@ export function getAvailablePlugins(): BackstagePlugin[] {
 
 function isBackstagePlugin(obj: unknown): obj is BackstagePlugin {
   if (obj !== null && typeof obj === 'object' && '$$type' in obj) {
-    return obj.$$type === 'backstage-plugin';
+    return obj.$$type === '@backstage/BackstagePlugin';
   }
   return false;
 }