docs(project structure): fix typo (#1972)

[skip ci]

Author: manuelro

docs/index.md

@@ -110,7 +110,7 @@ Overview
     ├── client
     │   ├── app                 - All of our app specific components go in here
     │   ├── assets              - Custom assets: fonts, images, etc…
-    │   ├── components          - Our reusable components, non-specific to to our app
+    │   ├── components          - Our reusable components, non-specific to our app
     │
     ├── e2e                     - Our protractor end to end tests
     │