stream_settings: Fix color of icon of the title in right column.

This commit fixes two things -

- We use the exact same color that is used for stream name in
day mode.

- Previously, we were passing black color explicitly to the
stream_privacy_icon template. This commit changes it to pass
different color in the night mode which is the same used for
stream name in night mode.

static/js/stream_settings_ui.js

@@ -40,7 +40,13 @@ import * as ui_report from "./ui_report";
 import * as util from "./util";
 
 export function set_right_panel_title(sub) {
-    $("#subscription_overlay .stream-info-title").html(render_selected_stream_title(sub));
+    let title_icon_color = "#333333";
+    if (settings_data.using_dark_theme()) {
+        title_icon_color = "#dddeee";
+    }
+    $("#subscription_overlay .stream-info-title").html(
+        render_selected_stream_title({sub, title_icon_color}),
+    );
 }
 
 export const show_subs_pane = {

static/templates/stream_settings/selected_stream_title.hbs

@@ -1,5 +1,5 @@
 {{> stream_privacy_icon
-  invite_only=invite_only
-  is_web_public=is_web_public
-  color="#000000" }}
-<span class="stream-name-title">{{name}}</span>
+  invite_only=sub.invite_only
+  is_web_public=sub.is_web_public
+  color=title_icon_color }}
+<span class="stream-name-title">{{sub.name}}</span>