_content/css: fix content aside section overlapping with footer

Fixes golang/go#58134

Change-Id: Ie2ef4d2b32d2f9eb834e0d7f909efecda4c08331
GitHub-Last-Rev: 8914d0f4f3
GitHub-Pull-Request: golang/website#190
Reviewed-on: https://go-review.googlesource.com/c/website/+/464015
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Suzy Mueller <suzmue@golang.org>

_content/css/styles.css

@@ -3644,7 +3644,7 @@ p.BackgroundQuote-body {
   flex-direction: column;
 }
 .UseCaseSubNav-anchorLinks--sticky {
-  position: fixed;
+  position: sticky;
   top: 2rem;
 }
 a.UseCase-anchorLink {