Enable simulcast statistics

Bug: webrtc:9547
Change-Id: I8b2920dacfac0085449a797f2831b86e2e5e65b5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173749
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Eldar Rello <elrello@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#31126}

api/peer_connection_interface.h

@@ -666,7 +666,7 @@ class RTC_EXPORT PeerConnectionInterface : public rtc::RefCountInterface {
     // Whether network condition based codec switching is allowed.
     absl::optional<bool> allow_codec_switching;
 
-    bool enable_simulcast_stats = false;
+    bool enable_simulcast_stats = true;
 
     //
     // Don't forget to update operator== if adding something.