fix typo

Author: RubyFore

_includes/css/grayscale.css

@@ -138,7 +138,7 @@ a:focus {
     padding: 100px 0;
     text-align: center;
     color: rgb(185, 189, 192);
-    background: url({{".../../img/IMG_3378.jpg") no-repeat bottom center scroll;
+    background: url(".../../img/IMG_3378.jpg") no-repeat bottom center scroll;
     background-color: {{ site.color.primary-dark }};
     -webkit-background-size: cover;
     -moz-background-size: cover;