_content/doc/go1.21: fix anchor name typo in link

Reported by Jochen Voss on the golang-nuts list

Change-Id: Ic0986948c13b30ce98a4bb763da883ab4fafd76b
Reviewed-on: https://go-review.googlesource.com/c/website/+/520215
Run-TryBot: Dmitri Shuralyov <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Eli Bendersky <[email protected]>

Author: eliben

_content/doc/go1.21.html

@@ -32,7 +32,7 @@ <h2 id="introduction">Introduction to Go 1.21</h2>
   Today we are releasing both the Go 1.21 language and its initial implementation, the Go 1.21.0 release.
   These notes refer to “Go 1.21”; tools like <code>go</code> <code>version</code> will report “<code>go1.21.0</code>”
   (until you upgrade to Go 1.21.1).
-  See “<a href="/doc/toolchain#versions">Go versions</a>” in the “Go Toolchains” documentation for details
+  See “<a href="/doc/toolchain#version">Go versions</a>” in the “Go Toolchains” documentation for details
   about the new version numbering.
 </p>