Closes issue #2040; disable block autoplay when using geckoview.

Block autoplay is unintentionally not disabled when using GeckoView.
If you look, you'll see autoplay blocking is attempted to be disabled
when using the system webview settings further down, but GeckoView
doesn't honor those settings; there's a GeckoView setting which
needs to be set to disable autoplay blocking.

app/src/gecko/java/org/mozilla/tv/firefox/webrender/WebRenderComponents.kt

@@ -50,6 +50,7 @@ class WebRenderComponents(applicationContext: Context, systemUserAgent: String)
                 runtimeSettingsBuilder.extras(extras)
             }
         }
+        runtimeSettingsBuilder.autoplayDefault(GeckoRuntimeSettings.AUTOPLAY_DEFAULT_ALLOWED)
 
         val runtime = GeckoRuntime.create(applicationContext,
                 runtimeSettingsBuilder.build())