website/_content/doc: add goroot tag example

Fixes golang/go#66448

Change-Id: I3f5e0f277c905381d55c5e95480f51f3004ee47a
GitHub-Last-Rev: 9675143
GitHub-Pull-Request: #276
Reviewed-on: https://go-review.googlesource.com/c/website/+/573735
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Cherry Mui <cherryyz@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

_content/doc/install/source.html

@@ -266,7 +266,7 @@ <h2 id="fetch">Fetch the repository</h2>
 
 <p>Change to the directory where you intend to install Go, and make sure
 the <code>goroot</code> directory does not exist. Then clone the repository
-and check out the latest release tag (<code class="versionTag">go1.12</code>,
+and check out the latest release tag or release branch (<code class="versionTag">go1.22.0</code>, or <code class="versionTag">release-branch.go1.22</code>,
 for example):</p>
 
 <pre>