Update WebRTC code version (2021-04-01T04:03:21).

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

Bug: None
Change-Id: I970473a3f532b88294a72859ed2534a6283256a2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/213521
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@{#33610}
diff --git a/call/version.cc b/call/version.cc
index c25b74a..7082a3e 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 2021-03-31T04:10:43";
+const char* const kSourceTimestamp = "WebRTC source stamp 2021-04-01T04:03:21";
 
 void LoadWebRTCVersionInRegister() {
   // Using volatile to instruct the compiler to not optimize `p` away even