Fixed simple typo

Author: wltjr1007

site/en/tutorials/_toc.yaml

@@ -136,7 +136,7 @@ toc:
   - title: "Translation with RNNs and attention"
     path: /text/tutorials/nmt_with_attention
     status: external
-  - title: "Translate text with a Transfromer"
+  - title: "Translate text with a Transformer"
     path: /text/tutorials/transformer
     status: external
   - title: "Image captioning"