Remove version switcher for Ddox navigation bar

Author: wilzbach

dpl-docs/views/layout.dt

@@ -147,12 +147,6 @@ html(lang='en-US')
           span.smallprint
             - if( haveVersion )
               | version #{version_name}
-              br
-              a(href='#{root_dir}library-prerelease/index.html') switch to pre-release version
-            - else
-              | pre-release version
-              br
-              a(href='#{root_dir}library/index.html') switch to latest release version
         p
           a(href="#{root_dir}#{ddox_dir}index.html") overview
         ul