docs(postcss): remove duplicated optimize example from README (#19938)

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## Summary

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your change solve the problem?

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Removed a duplicated optimize: { minify: false } example from
@tailwindcss/postcss README (doc-only, one file).

## Test plan

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Check the duplicate block is removed, the earlier optimize example still
exists, and only packages/@tailwindcss-postcss/README.md changed.

Author: pavan-sh

packages/@tailwindcss-postcss/README.md

@@ -110,17 +110,3 @@ export default {
 }
 ```
 
-You may also pass options to `optimize` to enable Lightning CSS but prevent minification:
-
-```js
-import tailwindcss from '@tailwindcss/postcss'
-
-export default {
-  plugins: [
-    tailwindcss({
-      // Enables Lightning CSS but disables minification
-      optimize: { minify: false },
-    }),
-  ],
-}
-```