Revert "update navi bar background to China Red for Spring Festival"

This reverts commit 799549e2050280b321acb4ba0da9abf3190738f7.

en_us/css/custom.css

@@ -1,3 +0,0 @@
-.viki-navbar {
-    background-color: #94070A;
-}

zh_cn/css/custom.css

@@ -1,3 +0,0 @@
-.viki-navbar {
-    background-color: #94070A;
-}