_content/doc: fix link in Go1.21 Release Notes

Change-Id: Iac71701b32ab529a0fa6f16fd711045093820112
GitHub-Last-Rev: cf450d727e
GitHub-Pull-Request: golang/website#238
Reviewed-on: https://go-review.googlesource.com/c/website/+/517115
Reviewed-by: t hepudds <thepudds1460@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: t hepudds <thepudds1460@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

_content/doc/go1.21.html

@@ -148,7 +148,7 @@ Do not send CLs removing the interior tags from such phrases.
   Go 1.21 now defines that if a goroutine is panicking and recover was called directly by a deferred
   function, the return value of recover is guaranteed not to be nil. To ensure this, calling panic
   with a nil interface value (or an untyped nil) causes a run-time panic of type
-  <a href="/runtime/#PanicNilError"><code>*runtime.PanicNilError</code></a>.
+  <a href="/pkg/runtime/#PanicNilError"><code>*runtime.PanicNilError</code></a>.
 </p>
 <p>
   To support programs written for older versions of Go, nil panics can be re-enabled by setting