docguide: Fix a typo

docguide/best_practices.md

@@ -136,6 +136,6 @@ to detailed prose:
 
 Do not write your own guide to a common Google technology or process. Link to it
 instead. If the guide doesn't exist or it's badly out of date, submit your
-updates to the appriopriate directory or create a package-level
+updates to the appropriate directory or create a package-level
 README.md. **Take ownership and don't be shy**: Other teams will usually welcome
 your contributions.