Remove commented out code and properly nest CSS again for .collapse

docs/assets/css/bootstrap.css

@@ -1985,16 +1985,6 @@ input[type="button"].btn-block {
   opacity: 1;
 }
 
-/*.collapse {
-  position: relative;
-  height: 0;
-  overflow: hidden;
-  .transition(height .35s ease);
-  &.in {
-    height: auto;
-  }
-}*/
-
 .collapse {
   position: relative;
   height: 0;

less/component-animations.less

@@ -11,22 +11,13 @@
   }
 }
 
-/*.collapse {
+.collapse {
   position: relative;
   height: 0;
   overflow: hidden;
   .transition(height .35s ease);
+
   &.in {
     height: auto;
   }
-}*/
-
-.collapse {
-  position: relative;
-  height: 0;
-  overflow: hidden;
-  .transition(height .35s ease);
-}
-.collapse.in {
-  height: auto;
 }