Bug 1589854 - Remove recent assert that gets triggered by latent bug. r=jib

Differential Revision: https://phabricator.services.mozilla.com/D49919

--HG--
extra : moz-landing-system : lando

dom/media/MediaDevices.cpp

@@ -165,7 +165,6 @@ already_AddRefed<Promise> MediaDevices::EnumerateDevices(CallerType aCallerType,
           },
           [this, self, p](const RefPtr<MediaMgrError>& error) {
             nsPIDOMWindowInner* window = GetWindowIfCurrent();
-            MOZ_DIAGNOSTIC_ASSERT(!window, "Should only fail after navigation");
             if (!window) {
               return;  // Leave Promise pending after navigation by design.
             }