Darken the orange buttons (#8219)

For WCAG 2.1, web components must have a 3:1 contrast ratio. This darkens both the "search" button in the header as well as the "copy" button for installation instructions.

Addresses #8195

Author: loic-sharma

src/Bootstrap/dist/css/bootstrap.css

@@ -166,7 +166,7 @@
 @btn-info-border:                darken(@btn-info-bg, 5%);
 
 @btn-warning-color:              #fff;
-@btn-warning-bg:                 @brand-warning;
+@btn-warning-bg:                 darken(@brand-warning, 5.75%);
 @btn-warning-border:             darken(@btn-warning-bg, 5%);
 
 @btn-danger-color:               #fff;
@@ -874,4 +874,4 @@
 //** Horizontal line color.
 @hr-border:                   @gray-lighter;
 
-@info-bg:                     #fff4ce;
+@info-bg:                     #fff4ce;