fix(cssnano-preset): disable CSS counter minification (facebook#11487)

Co-authored-by: Sébastien Lorber <slorber@users.noreply.github.com>

Author: YDKK

packages/docusaurus-cssnano-preset/src/index.ts

@@ -13,6 +13,9 @@ const preset: typeof advancedBasePreset = function preset(opts) {
   const advancedPreset = advancedBasePreset({
     autoprefixer: {add: false},
     discardComments: {removeAll: true},
+    // See CodeBlock custom line number bug: https://github.com/facebook/docusaurus/pull/11487
+    /* cSpell:ignore Idents */
+    reduceIdents: {counter: false},
     /* cSpell:ignore zindex */
     zindex: false,
     ...opts,

website/_dogfooding/_pages tests/code-block-tests.mdx

@@ -226,6 +226,13 @@ function PageLayout(props) {
 }
 ```
 
+```jsx showLineNumbers=4
+function PageLayout(props) {
+  // highlight-next-line
+  return <Layout title="Awesome Docusaurus page" description="Test Test Test Test Test Test Test Test Test Test Test Test Test Test ">;
+}
+```
+
 ```jsx {1,3,6} showLineNumbers
 function PageLayout(props) {
   console.log(