docs: fix installation version of packages (#8177)

www/apps/resources/app/architectural-modules/cache/in-memory/page.mdx

@@ -25,7 +25,7 @@ The In-Memory Cache Module is installed by default in your application.
 To install the In-Memory Cache Module, run the following command in the directory of your Medusa application:
 
 ```bash npm2yarn
-npm install @medusajs/cache-inmemory
+npm install @medusajs/cache-inmemory@preview
 ```
 
 Next, add the module into the `modules` property of the exported object in `medusa-config.js`: