doc: add release notes about bootstrap toolchain version

For #61422.

Change-Id: Ie0d3c05752d29aa65983add85935d2505560ec55
Reviewed-on: https://go-review.googlesource.com/c/go/+/546029
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

doc/go1.22.html

@@ -108,6 +108,14 @@ <h2 id="linker">Linker</h2>
   TODO: complete this section, or delete if not needed
 </p>
 
+<h2 id="bootstrap">Bootstrap</h2>
+
+<p>
+  As mentioned in the <a href="/doc/go1.20#bootstrap">Go 1.20 release notes</a>, Go 1.22 now requires
+  the final point release of Go 1.20 or later for bootstrap.
+  We expect that Go 1.24 will require the final point release of Go 1.22 or later for bootstrap.
+</p>
+
 <h2 id="library">Core library</h2>
 
 <h3 id="minor_library_changes">New math/rand/v2 package</h3>