Fix navigation border color for dark theme.

Author: grandsilence

styles/index.styl

@@ -101,7 +101,7 @@ p a code
 
 hr,
 .page-nav .inner
-  border-top-color var(--borderColor)
+  border-top-color var(--borderColor) !important
 
 tr
   border-top-color var(--tableBorderColor)