docs: fix typo in docs-introduction (#9267)

website/docs/guides/docs/docs-introduction.mdx

@@ -47,6 +47,7 @@ Assume that you have the following in your configuration:
 module.exports = {
   // ...
   presets: [
+    [
       '@docusaurus/preset-classic',
       {
         docs: {
@@ -58,6 +59,7 @@ module.exports = {
         // ...
       },
     ],
+  ],
 };
 ```
 
@@ -67,6 +69,7 @@ To enter docs-only mode, change it to like this:
 module.exports = {
   // ...
   presets: [
+    [
       '@docusaurus/preset-classic',
       {
         docs: {
@@ -79,6 +82,7 @@ module.exports = {
         // ...
       },
     ],
+  ],
 };
 ```