remove custom css support

* user can clone head into <site root>/layouts/partials/head.html
and add custom resources and assets according to wish

layouts/partials/head.html

@@ -35,7 +35,6 @@
 <link href="{{ $profileMode.Permalink }}" integrity="{{ $profileMode.Data.Integrity }}" rel="preload stylesheet"
     as="style">
 {{end}}
-<link href="{{ "custom.css" | absURL }}" rel="stylesheet">
 <!-- Favicons -->
 <link rel="apple-touch-icon" href="{{ "apple-touch-icon.png" | absURL }}">
 <link rel="icon" href="{{ "favicon.ico" | absURL }}">

static/custom.css

@@ -1 +0,0 @@
-/* Place a custom css file in your own project to use this. */