Clean up header gradient

sass/partials/common/_sprites.scss

@@ -173,14 +173,10 @@ input[name*="search"] {
 #header {
   background-image: $sprite-horizontal;
   background-repeat: repeat-x;
-}
-
-#header {
   background-position: 0 -1088px;
-}
-
-body.front #header {
-  background-position: 0 0;
+  body.front.drupalorg-site-main & {
+    background-position: 0 0;
+  }
 }
 
 // General sprites