Update WebRTC code version (2021-05-10T04:02:04).

TBR=webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com,mbonadei@webrtc.org

Bug: None
Change-Id: I1d163342579cf259be1635570ceb68cb5f70084e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/218080
Reviewed-by: webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com <webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com>
Commit-Queue: webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com <webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#33962}

call/version.cc

diff --git a/call/version.cc b/call/version.cc
index 7a89510..dd3d90d 100644
--- a/call/version.cc
+++ b/call/version.cc
@@ -13,7 +13,7 @@
 namespace webrtc {
 
 // The timestamp is always in UTC.
-const char* const kSourceTimestamp = "WebRTC source stamp 2021-05-09T04:02:14";
+const char* const kSourceTimestamp = "WebRTC source stamp 2021-05-10T04:02:04";
 
 void LoadWebRTCVersionInRegister() {
   // Using volatile to instruct the compiler to not optimize `p` away even