Fixed: Refresh backup list on deletion

(cherry picked from commit 3b00112447361b19c04851a510e63f812597a043)

src/Radarr.Api.V3/System/Backup/BackupController.cs

@@ -50,7 +50,7 @@ namespace Radarr.Api.V3.System.Backup
         }
 
         [RestDeleteById]
-        public void DeleteBackup(int id)
+        public object DeleteBackup(int id)
         {
             var backup = GetBackup(id);
 
@@ -67,6 +67,8 @@ namespace Radarr.Api.V3.System.Backup
             }
 
             _diskProvider.DeleteFile(path);
+
+            return new { };
         }
 
         [HttpPost("restore/{id:int}")]