update assets from bootstrap@3.3.7

assets/less/bootstrap/close.less

@@ -1,7 +1,10 @@
+// stylelint-disable property-no-vendor-prefix
+
 //
 // Close icons
 // --------------------------------------------------
 
+
 .close {
   float: right;
   font-size: (@font-size-base * 1.5);
@@ -9,14 +12,14 @@
   line-height: 1;
   color: @close-color;
   text-shadow: @close-text-shadow;
-  .opacity(0.2);
+  .opacity(.2);
 
   &:hover,
   &:focus {
     color: @close-color;
     text-decoration: none;
     cursor: pointer;
-    .opacity(0.5);
+    .opacity(.5);
   }
 
   // Additional properties for button version
@@ -29,5 +32,6 @@
     background: transparent;
     border: 0;
     -webkit-appearance: none;
+    appearance: none;
   }
 }