_content: fix duplicate github icon

Fixes golang/go#58555

Change-Id: I36788aabbe09c4e5f343ae88d94392c202ff144f
Reviewed-on: https://go-review.googlesource.com/c/website/+/469815
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
diff --git a/_content/css/styles.css b/_content/css/styles.css
index 303fa69..23f7f8f 100644
--- a/_content/css/styles.css
+++ b/_content/css/styles.css
@@ -766,13 +766,6 @@
     filter: invert(1);
   }
 }
-[data-theme='dark'] .Header-menuItem a.Header-socialIcon.Header-socialIcon-dark {
-  display: inline-flex;
-}
-[data-theme='dark'] .Header-menuItem a.Header-socialIcon.Header-socialIcon-light {
-  display: none;
-}
-/* End nav */
 .Article {
   color: var(--color-text);
   margin: 0 auto 1.875rem;
diff --git a/_content/site.tmpl b/_content/site.tmpl
index 5b5ea62..52ff568 100644
--- a/_content/site.tmpl
+++ b/_content/site.tmpl
@@ -83,12 +83,7 @@
                     {{- if .socialIconsList}}
                       <div class="Header-socialIcons">
                         {{ range .socialIconsList }}
-                        {{ if .darkImg }}
-                        <a class="Header-socialIcon Header-socialIcon-light" href="{{.url}}"><img src="/images/logos/social/{{.img}}" /></a>
-                        <a class="Header-socialIcon Header-socialIcon-dark" href="{{.url}}"><img src="/images/logos/social/{{.darkImg}}" /></a>
-                        {{else}}
                         <a class="Header-socialIcon" href="{{.url}}"><img src="/images/logos/social/{{.img}}" /></a>
-                        {{end}}
                         {{- end}}
                       </div>
                     {{- end}}