Fix color of /about/more link anchors (#7618)

app/javascript/styles/mastodon/about.scss

@@ -396,7 +396,7 @@ $small-breakpoint: 960px;
         display: flex;
         justify-content: center;
         align-items: center;
-        color: $ui-primary-color;
+        color: $darker-text-color;
         text-decoration: none;
         padding: 12px 16px;
         line-height: 32px;