Clarify extra-deps doc #1734

Author: mgsloan

doc/yaml_configuration.md

@@ -74,7 +74,7 @@ packages:
 
 This is a list of package identifiers for additional packages from upstream to
 be included. This is usually used to augment an LTS Haskell or Stackage Nightly
-snapshot with a package that is not present or is at an older version than you
+snapshot with a package that is not present or is at an different version than you
 wish to use.
 
 ```yaml