Link to correct version of SanitizationFilter API docs for whitelist

[ci skip]

doc/user/markdown.md

@@ -590,7 +590,7 @@ Quote break.
 
 You can also use raw HTML in your Markdown, and it'll mostly work pretty well.
 
-See the documentation for HTML::Pipeline's [SanitizationFilter](http://www.rubydoc.info/gems/html-pipeline/HTML/Pipeline/SanitizationFilter#WHITELIST-constant) class for the list of allowed HTML tags and attributes.  In addition to the default `SanitizationFilter` whitelist, GitLab allows `span` elements.
+See the documentation for HTML::Pipeline's [SanitizationFilter](http://www.rubydoc.info/gems/html-pipeline/1.11.0/HTML/Pipeline/SanitizationFilter#WHITELIST-constant) class for the list of allowed HTML tags and attributes.  In addition to the default `SanitizationFilter` whitelist, GitLab allows `span` elements.
 
 ```no-highlight
 <dl>