Disable RTD search.

It's completely broken anyway.

docs/_templates/layout.html

@@ -26,4 +26,15 @@
   {% if pagename == 'index' %}
   </div>
   {% endif %}
+
+  {%- if readthedocs %}
+  <script>
+    if (typeof READTHEDOCS_DATA !== 'undefined') {
+        if (!READTHEDOCS_DATA.features) {
+          READTHEDOCS_DATA.features = {};
+        }
+        READTHEDOCS_DATA.features.docsearch_disabled = true;
+      }
+    </script>
+  {%- endif %}
 {%- endblock %}