Update WebRTC code version (2023-06-20T04:03:02).

Bug: None
Change-Id: I6bc533128e5303bfc7a54c3f879b899e0550e2b2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/309425
Bot-Commit: 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@{#40310}

call/version.cc

diff --git a/call/version.cc b/call/version.cc
index b4d5207..2d1db90 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 2023-06-17T04:02:25";
+const char* const kSourceTimestamp = "WebRTC source stamp 2023-06-20T04:03:02";
 
 void LoadWebRTCVersionInRegister() {
   // Using volatile to instruct the compiler to not optimize `p` away even