static/shared: update brand guidelines url in footer

Updates #58412.

Change-Id: Ibda66b252c92a90a3c3af669b959cd1b76d06364
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/638496
kokoro-CI: kokoro <[email protected]>
Reviewed-by: Sean Liao <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Sean Liao <[email protected]>
Reviewed-by: Junyang Shao <[email protected]>

Author: alexandear

static/shared/footer/footer.tmpl

@@ -71,7 +71,7 @@
             data-gtmc="footer link">
           Release Notes
         </a>
-        <a href="https://blog.golang.org/go-brand" class="go-Footer-link" data-gtmc="footer link">
+        <a href="https://go.dev/brand" class="go-Footer-link" data-gtmc="footer link">
           Brand Guidelines
         </a>
         <a href="https://go.dev/conduct" class="go-Footer-link" data-gtmc="footer link">