remove nipponUltraBlue

Author: isoos

pkg/web_css/lib/src/_variables.scss

@@ -151,7 +151,6 @@
   --pub-color-darkBlack:       #121317;
   --pub-color-darkGunmetal:    #242b32;
   --pub-color-darkGray:        #2f3034; /* derived from dark black by making it lighter */
-  --pub-color-nipponUltraBlue: #23607f;
   --pub-color-darkSteelBlue:   #144466;
 
   --pub-neutral-bgColor:       var(--pub-color-darkBlack);