Do not disable metrics by default.

Starting from [1] metrics are optional but by default they should be
enabled.

[1] - https://webrtc-review.googlesource.com/c/src/+/161043

Bug: webrtc:11144
Change-Id: I0b22e2c59ff9df73a82f354997f073b6da028875
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161728
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30057}
diff --git a/webrtc.gni b/webrtc.gni
index 513d5fc..fe0b1b2 100644
--- a/webrtc.gni
+++ b/webrtc.gni
@@ -254,7 +254,7 @@
   rtc_disable_check_msg = false
 
   # Set this to true to disable webrtc metrics.
-  rtc_disable_metrics = true
+  rtc_disable_metrics = false
 }
 
 # Make it possible to provide custom locations for some libraries (move these