Undo the collapse visibility changes since it breaks our collapse plugin

dist/css/bootstrap.css

@@ -3178,11 +3178,9 @@ input[type="button"].btn-block {
 }
 .collapse {
   display: none;
-  visibility: hidden;
 }
 .collapse.in {
   display: block;
-  visibility: visible;
 }
 tr.collapse.in {
   display: table-row;

less/component-animations.less

@@ -17,9 +17,8 @@
 
 .collapse {
   display: none;
-  visibility: hidden;
 
-  &.in      { display: block; visibility: visible; }
+  &.in      { display: block; }
   tr&.in    { display: table-row; }
   tbody&.in { display: table-row-group; }
 }