Update document-settings.mdx

Fix typo

Author: franxois

src/docs/documentation/general/document-settings.mdx

@@ -10,7 +10,7 @@ menu: General
 Document settings can be something simple, but powerful. They should be defined in the top of the `.mdx`
 using yaml and can be used to change whatever you want by passing this config to your theme.
 
-By default the document has just tree properties that can't be overrided:
+By default the document has just three properties that can't be overrided:
 
 ```markdown
 ---