Removing duplicate custom-jekyll js

After docsy theme got merged these scripts aren't needed anymore.  Confirmed
after removing it (and all `<script>` references to it) the tooltip
functionality is still there.
Also removed the reference in `config.toml` to it, which may have stripped some
dangling whitespace.

layouts/partials/head.html

@@ -84,6 +84,5 @@
 {{ end }}
 
 <script src="{{ "js/script.js" | relURL }}"></script>
-<script src="{{ "js/custom-jekyll/tags.js" | relURL }}"></script>
 {{ with .Params.js }}{{ range (split . ",") }}<script src="{{ (trim . " ") | relURL }}"></script><!-- custom js added -->
 {{ end }}{{ else }}<!-- no custom js detected -->{{ end }}