fix: deduplicate discovered backend features

Signed-off-by: Stanislav C <150145013+stanislav-c@users.noreply.github.com>

.changeset/afraid-streets-pay.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-defaults': patch
+---
+
+Deduplicate discovered features discovered with discoveryFeatureLoader

packages/backend-defaults/src/PackageDiscoveryService.ts

@@ -175,6 +175,6 @@ export class PackageDiscoveryService {
       }
     }
 
-    return { features };
+    return { features: Array.from(new Set(features)) };
   }
 }