night-mode: don't override search background color

The color of the top-navigation for "light" and "night" mode is the
same, so we don't need to override the color (for now). The old override
used a hue that was slightly out of tone with the rest of the theme.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

_scss/_night-mode.scss

@@ -64,15 +64,6 @@ a {
     }
     .nav-secondary {
         background-color: $bg-header-night;
-
-        .search-form input[type=search] {
-          background-color: rgba(76, 76, 76, 0.47);
-          color: $white;
-
-          & :focus {
-            background-color: rgba(255, 255, 255, 0.17);
-          }
-        }
     }
     .breadcrumb {
         background-color: $dark-grey-100;