SplitSettings cleanup: Remove use of showOSSettings flag from basic_page

Bug: 986596
Change-Id: I289faebea8b6e7300394045c4ede267d2b2d2fa4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992620Reviewed-by: Dan Beam <dbeam@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729545}

chrome/browser/resources/settings/basic_page/basic_page.js

@@ -233,11 +233,6 @@ Polymer({
     if (!this.prefs || !this.currentRoute_) {
       return;
     }
-    // Don't show the banner when SplitSettings is disabled (and hence this page
-    // is already showing OS settings).
-    if (loadTimeData.getBoolean('showOSSettings')) {
-      return false;
-    }
     const showPref = /** @type {boolean} */ (
         this.getPref('settings.cros.show_os_banner').value);