No Temasys alert on mobile Web

css/unsupported-browser/_unsupported-mobile-browser.scss

@@ -67,3 +67,16 @@
         }
     }
 }
+
+// Temasys provide lib-jitsi-meet/modules/RTC/adapter.screenshare.js which
+// detects whether the browser supports WebRTC. If the browser does not support
+// WebRTC, it displays an alert in the form of a yellow bar at the top of the
+// page. The alert notifies the user that the browser does not support WebRTC
+// and, if Temasys provide a plugin for the browser, the alert contains a button
+// to initiate installing the browser. When Temasys do not provide a plugin for
+// the browser, we do not want the alert on the unsupported-browser page because
+// the notification about the lack of WebRTC support is the whole point of the
+// unsupported-browser page.
+iframe[name="adapterjs-alert"] {
+    display: none;
+}