Refresh rtc_base/OWNERS.

This CL removes two owners who don't actively work on WebRTC and adds
mbonadei@.

Bug: None
Change-Id: I771e3ce2f97e20d043e074428829d05b39154025
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/196650
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32833}
diff --git a/rtc_base/OWNERS b/rtc_base/OWNERS
index 2bef3d7..ce7968c 100644
--- a/rtc_base/OWNERS
+++ b/rtc_base/OWNERS
@@ -1,9 +1,8 @@
 hta@webrtc.org
 juberti@webrtc.org
 mflodman@webrtc.org
-qingsi@webrtc.org
-sergeyu@chromium.org
 tommi@webrtc.org
+mbonadei@webrtc.org
 
 per-file rate_statistics*=sprang@webrtc.org
 per-file rate_statistics*=stefan@webrtc.org