Fixes Issue #16371 Carousel control is vertically off center for small screens

less/carousel.less

@@ -130,6 +130,7 @@
   .glyphicon-chevron-right {
     position: absolute;
     top: 50%;
+    margin-top: -10px;
     z-index: 5;
     display: inline-block;
   }
@@ -147,7 +148,6 @@
   .icon-next {
     width:  20px;
     height: 20px;
-    margin-top: -10px;
     line-height: 1;
     font-family: serif;
   }