[release-branch.go1.21] go1.21rc4

Change-Id: I4a166f3d04747703f2c0b3c3f245d9cde44f3068
Reviewed-on: https://go-review.googlesource.com/c/go/+/514777
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Gopher Robot <gobot@golang.org>
Auto-Submit: Gopher Robot <gobot@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/VERSION b/VERSION
index e44eb82..55b46a5 100644
--- a/VERSION
+++ b/VERSION
@@ -1,2 +1,2 @@
-go1.21rc3
-time 2023-07-13T19:00:35Z
+go1.21rc4
+time 2023-08-01T22:09:51Z