Docs: remove duplicate "available" (#6380)

Merge pull request 6380

docs/_docs/permalinks.md

@@ -354,7 +354,7 @@ As with posts, if you use a permalink style that omits the `.html` file extensio
 
 By default, collections follow a similar structure in the `_site` folder as pages, except that the path is prefaced by the collection name. For example: `collectionname/mypage.html`. For permalink settings that omit the file extension, the path would be `collection_name/mypage/index.html`.
 
-Collections have their own way of setting permalinks. Additionally, collections have unique template variables available available (such as `path` and `output_ext`). See the [Configuring permalinks for collections](../collections/#permalinks) in Collections for more information.
+Collections have their own way of setting permalinks. Additionally, collections have unique template variables available (such as `path` and `output_ext`). See the [Configuring permalinks for collections](../collections/#permalinks) in Collections for more information.
 
 ## Flattening pages in \_site on build