CR: Correct configuration example

Kieranties · Kieranties · commit b82c2977a899 · 2019-04-26T09:09:15.000+01:00
diff --git a/docs/configuration.md b/docs/configuration.md
@@ -48,7 +48,7 @@ commit-date-format: 'yyyy-MM-dd'
 ignore:
   sha: []
   commits-before: yyyy-MM-ddTHH:mm:ss
-merge-messages: {}
+merge-message-formats: {}
 ```
 
 And the description of the available options are:
