Update README.md (#25834)

_toctree.yml file. broken link, now fixed.

docs/README.md

@@ -84,7 +84,7 @@ The `preview` command only works with existing doc files. When you add a complet
 Accepted files are Markdown (.md or .md).
 
 Create a file with its extension and put it in the source directory. You can then link it to the toc-tree by putting
-the filename without the extension in the [`_toctree.yml`](https://github.com/huggingface/transformers/blob/main/docs/source/_toctree.yml) file.
+the filename without the extension in the [`_toctree.yml`](https://github.com/huggingface/transformers/blob/main/docs/source/en/_toctree.yml) file.
 
 ## Renaming section headers and moving sections