docs: 修改canonical地址

sample.html

@@ -5,7 +5,7 @@
         <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
         <link rel="stylesheet" type="text/css" href="https://c.mipcdn.com/static/v1/mip.css">
         <!--TODO: canonical href需要替换成原页面url-->
-        <link rel="canonical" href="https://m.baidu.com/demo.html">
+        <link rel="canonical" href="https://www.mipengine.org/test_xxx.html">
         <title>MIP页Demo效果</title>
         <!--TODO: 替换样式-->
         <style mip-custom>