Include a warning in the readme about sample data being persistent in the db

Just a small thing that might save many people some time:

In this repos readme, where it's stated that "Installing sample data is optional." adding a warning like the one that's on [adobes official experience league documentation](https://experienceleague.adobe.com/en/docs/commerce-operations/installation-guide/next-steps/sample-data/overview) might save a lot of people some minor hassle when having to purge the sample data from their production setups that they might have accidentally installed it to.

The original warning text is this:
_WARNING
You cannot uninstall sample data. Use sample data only to learn about how Adobe Commerce works. Avoid doing any development in a system in which you installed sample data._

Without proper information about the sample data being permanent in the database the "Uninstall" section further down in the readme where it says "To remove the sample data modules from the code base, run one of the following commands..." is misleading and causing people to install sampledata in the belief that removing it later is just one command away.

Thanks for your attention - keep up the great work!

Edit the repository README where it says that installing sample data is optional and where the Uninstall section explains removing the sample data modules. Add a clear warning that installed sample data persists in the database and cannot be uninstalled by removing the modules, using the linked Adobe documentation for context. Done means readers are warned before installation and the Uninstall wording is no longer misleading.

Written by the indexing model from the issue text.