Merge pull request #4572 from nikolaynizruhin/patch-1

Remove sass variables which does not exist in bootstrap 4

resources/assets/sass/_variables.scss

@@ -6,13 +6,3 @@ $body-bg: #f5f8fa;
 $font-family-sans-serif: "Raleway", sans-serif;
 $font-size-base: 0.9rem;
 $line-height-base: 1.6;
-$text-color: #636b6f;
-
-// Navbar
-$navbar-default-bg: #fff;
-
-// Buttons
-$btn-default-color: $text-color;
-
-// Panels
-$panel-default-heading-bg: #fff;