docs: rename incorrect usage of the cloud storage plugin to align with the imported module in storage-adapters.mdx (#11475)

### What?

The cloudStorage plugin was used incorrectly in the code snippet. While
`cloudStoragePlugin` was imported, `cloudStorage` was mistakenly used
within the plugin array.

### How?

Renamed the incorrect usage of `cloudStorage` to `cloudStoragePlugin` to
align with the imported module.

Author: jhb-dev

docs/upload/storage-adapters.mdx

@@ -424,7 +424,7 @@ import { cloudStoragePlugin } from '@payloadcms/plugin-cloud-storage'
 
 export default buildConfig({
   plugins: [
-    cloudStorage({
+    cloudStoragePlugin({
       collections: {
         'my-collection-slug': {
           adapter: theAdapterToUse, // see docs for the adapter you want to use