i18n: Use double lowdash instead of handlebars.

We do not allow handlebars within {{#tr}}{{/tr}}.

static/js/settings.js

@@ -90,6 +90,7 @@ function _setup_page() {
         zuliprc: 'zuliprc',
         flaskbotrc: 'flaskbotrc',
         timezones: moment.tz.names(),
+        server_uri: page_params.server_uri,
     });
 
     $(".settings-box").html(settings_tab);

static/templates/settings/bot-settings.handlebars

@@ -3,7 +3,7 @@
         <p class="bot-settings-note padded-container">
             {{#tr this}}
             Looking for our <a href="/integrations" target="_blank">Integrations</a>
-            or <a href="{{ server_uri }}/api" target="_blank">API</a> documentation?
+            or <a href="__server_uri__/api" target="_blank">API</a> documentation?
             {{/tr}}
         </p>