Simplify code for 'cover' example by using utility classes. (#28986)

site/content/docs/4.3/examples/cover/cover.css

@@ -2,12 +2,6 @@
  * Globals
  */
 
-/* Links */
-a,
-a:focus,
-a:hover {
-  color: #fff;
-}
 
 /* Custom default button */
 .btn-secondary,
@@ -15,8 +9,6 @@ a:hover {
 .btn-secondary:focus {
   color: #333;
   text-shadow: none; /* Prevent inheritance from `body` */
-  background-color: #fff;
-  border: .05rem solid #fff;
 }
 
 
@@ -24,15 +16,7 @@ a:hover {
  * Base structure
  */
 
-html,
 body {
-  height: 100%;
-  background-color: #333;
-}
-
-body {
-  display: flex;
-  color: #fff;
   text-shadow: 0 .05rem .1rem rgba(0, 0, 0, .5);
   box-shadow: inset 0 0 5rem rgba(0, 0, 0, .5);
 }
@@ -45,13 +29,6 @@ body {
 /*
  * Header
  */
-.masthead {
-  margin-bottom: 2rem;
-}
-
-.masthead-brand {
-  margin-bottom: 0;
-}
 
 .nav-masthead .nav-link {
   padding: .25rem 0;
@@ -74,32 +51,3 @@ body {
   color: #fff;
   border-bottom-color: #fff;
 }
-
-@media (min-width: 48em) {
-  .masthead-brand {
-    float: left;
-  }
-  .nav-masthead {
-    float: right;
-  }
-}
-
-
-/*
- * Cover
- */
-.cover {
-  padding: 0 1.5rem;
-}
-.cover .btn-lg {
-  padding: .75rem 1.25rem;
-  font-weight: 700;
-}
-
-
-/*
- * Footer
- */
-.mastfoot {
-  color: rgba(255, 255, 255, .5);
-}