FilterTags: Adjust relative URL reference

With context-aware includes, all relative URLs should now be with
respect to the file that contains the relative URLs, instead of
being with respect to the files that are expected to include them.

FilterTags needs to be updated so that the reference to Hiding
Tags is with respect to its location in userGuide/plugins/.

docs/userGuide/plugins/filterTags.mbdf

@@ -79,7 +79,7 @@ Alternatively, you can specify tags to render for a page in the front matter.
 ```
 </span>
 
-Tags in `site.json` will be merged with the ones in the front matter, and are processed after front matter tags. See [Hiding Tags](userGuide/tweakingThePageStructure.html#hiding-tags) for more information.
+Tags in `site.json` will be merged with the ones in the front matter, and are processed after front matter tags. See [Hiding Tags](../tweakingThePageStructure.html#hiding-tags) for more information.
 
 #### Advanced Tagging Tips