luci-app-statistics: remove non-functional links from graphs

The statistics graphs on the pages with multiple data sources
have contained links to the data sources, but those links
have not worked. Remove the links as they are unnecessary.

This commit fixes #1006

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

applications/luci-app-statistics/luasrc/view/public_statistics/graph.htm

@@ -29,9 +29,7 @@
 
 <div style="text-align: center">
 	<% for i, img in ipairs(images) do %>
-		<% if is_index then %><a href="<%=pcdata(images[img])%>"><% end %>
 		<img src="<%=REQUEST_URI%>?img=<%=img%>&#38;host=<%=current_host%>" />
-		<% if is_index then %></a><% end %>
 		<br />
 	<% end %>
 </div>