Fixed: Refresh backup list on deletion

Fixes #2300

src/Prowlarr.Api.V1/System/Backup/BackupController.cs

@@ -51,7 +51,7 @@ namespace Prowlarr.Api.V1.System.Backup
         }
 
         [RestDeleteById]
-        public void DeleteBackup(int id)
+        public object DeleteBackup(int id)
         {
             var backup = GetBackup(id);
 
@@ -68,6 +68,8 @@ namespace Prowlarr.Api.V1.System.Backup
             }
 
             _diskProvider.DeleteFile(path);
+
+            return new { };
         }
 
         [HttpPost("restore/{id:int}")]