Sanitize translations instead of using _html

Using the `_html` suffix in an i18n key is the same as using `html_safe`
on it, which means that translation could potentially be used for XSS
attacks.

app/views/debates/index.html.erb

@@ -18,7 +18,9 @@
             <p>
               <%= page_entries_info @debates %>
               <% if !@advanced_search_terms %>
-                <%= t("debates.index.search_results_html", count: @debates.size, search_term: @search_terms) %>
+                <%= sanitize(
+                  t("debates.index.search_results", count: @debates.size, search_term: @search_terms)
+                ) %>
               <% end %>
             </p>
           <% elsif @tag_filter %>