Update docs/contributing/index.md

Co-authored-by: Katja Süss <[email protected]>

Author: stevepiercy

docs/contributing/index.md

@@ -117,7 +117,7 @@ This practice differs depending on whether you are making contributions to only
 
 This section describes how to make contributions to files in the `plone/documentation` repository only, and excludes `plone/volto/docs` files.
 
-1.  From the project root directory, synch your local `6-dev` branch with its remote.
+1.  From the project root directory, sync your local `6-dev` branch with its remote.
     You might need to resolve conflicts.
 
     ```shell