Update WebRTC code version (2021-09-29T04:04:04).

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

Bug: None
Change-Id: Ic65ea08c6def4c276b1b7505d6e8a4608f10dd18
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/233281
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/main@{#35114}
diff --git a/call/version.cc b/call/version.cc
index 3b000d7..d887ac1 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 2021-09-28T04:02:20";
+const char* const kSourceTimestamp = "WebRTC source stamp 2021-09-29T04:04:04";
 
 void LoadWebRTCVersionInRegister() {
   // Using volatile to instruct the compiler to not optimize `p` away even