Update buttons.

scss/bootstrap/_buttons.scss

@@ -13,7 +13,7 @@
     &:hover, &:active, &:focus {
       color: $black;
       background-color: $gray-300;
-      border-color: $gray-300;
+      border-color: $gray-400;
     }
   }
 
@@ -58,7 +58,7 @@
     &:hover {
       color: $black;
       background-color: $gray-200;
-      border-color: $gray-200;
+      border-color: $gray-400;
     }
   }
 }