feat(date-picker): [date-picker] Optimize demo style

Author: Youyou-smiles

Diff for: examples/sites/demos/pc/app/date-picker/custom-suffix-icon-composition-api.vue

@@ -19,6 +19,6 @@ const IconMinus = iconMinus()
 }
 
 .my-date-picker {
-  background: #ddd;
+  background: #f0f0f0;
 }
 </style>

Diff for: examples/sites/demos/pc/app/date-picker/custom-suffix-icon.vue

@@ -27,6 +27,6 @@ export default {
 }
 
 .my-date-picker {
-  background-color: #ddd;
+  background-color: #f0f0f0;
 }
 </style>