chore(Skeleton): remove animation-delay

Author: anlyyao

src/skeleton/skeleton.less

@@ -80,12 +80,12 @@
           @skeleton-animation-gradient,
           rgba(255, 255, 255, 0%)
         );
-        animation: t-skeleton--gradient 1.5s linear 2s infinite;
+        animation: t-skeleton--gradient 1.5s linear 0s infinite;
       }
     }
 
     &-flashed {
-      animation: t-skeleton--flashed 2s linear 2s infinite;
+      animation: t-skeleton--flashed 2s linear 0s infinite;
     }
   }