nixos/doc/release-notes-2505: fix table formatting for system.build

Author: leona-ya

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -452,7 +452,7 @@ Alongside many enhancements to NixOS modules and general system improvements, th
   Names are now known at evaluation time and customizable via the new options `image.baseName`, `image.extension`, `image.fileName` and `image.filePath` with the latter returning a path relative to the derivations out path (e.g. `iso/${image.fileName` for iso images).
 
   | `system.build` Option    | Old Filename                                               | New Filename                                                    |
-  |--------------------------+------------------------------------------------------------+-----------------------------------------------------------------|
+  | ------------------------ | ---------------------------------------------------------- | ----------------------------------------------------------------|
   | amazonImage              | nixos-amazon-image-25.05pre-git-x86_64-linux.vhd           | nixos-image-amazon-25.05pre-git-x86_64-linux.vhd                |
   | azureImage               | disk.vhd                                                   | nixos-image-azure-25.05pre-git-x86_64-linux.vhd                 |
   | digitalOceanImage        | nixos.qcow2.gz                                             | nixos-image-digital-ocean-25.05pre-git-x86_64-linux.qcow2.gz    |