Remove reference to the unused horsey CSS

Author: nvasudevan

layouts/404.html

@@ -11,7 +11,6 @@
     <link href="{{"css/hybrid.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
     <link href="{{"css/featherlight.min.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
     <link href="{{"css/perfect-scrollbar.min.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
-    <link href="{{"css/horsey.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
     <link href="{{"css/theme.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
     <link href="{{"css/hugo-theme.css" | relURL}}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="stylesheet">
     {{with .Site.Params.themeVariant}}