doc/go1.19: use correct link to sync/atomic docs

For golang#51400
Fixes golang#53453

Change-Id: Ie11182a16299cf26d03970d6aa9bfe03caa56ea4
Reviewed-on: https://go-review.googlesource.com/c/go/+/413235
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

doc/go1.19.html

@@ -35,7 +35,7 @@ <h2 id="mem">Memory Model</h2>
   the memory model used by C, C++, Java, JavaScript, Rust, and Swift.
   Go only provides sequentially consistent atomics, not any of the more relaxed forms found in other languages.
   Along with the memory model update,
-  Go 1.19 introduces <a href="#sync/atomic">new types in the <code>sync/atomic</code> package</a>
+  Go 1.19 introduces <a href="#atomic_types">new types in the <code>sync/atomic</code> package</a>
   that make it easier to use atomic values, such as
   <a href="/pkg/sync/atomic/#Int64">atomic.Int64</a>
   and