docs: update banner wording

Author: idleberg

README.md

@@ -28,7 +28,7 @@ gulp.task('lint', done => {
 ```
 
 > [!IMPORTANT]
-> This plugin is now pure ESM. [Read how to migrate your `Gulpfile`](https://gist.github.com/noraj/007a943dc781dc8dd3198a29205bae04). Alternatively, you can continue using the an *unsupported* 1.x version.
+> This plugin is now pure ESM. [Read how to migrate your `Gulpfile`](https://gist.github.com/noraj/007a943dc781dc8dd3198a29205bae04). Alternatively, you can continue using an *unsupported* 1.x version.
 
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