Issue description:
RH-SSO 7.6 documentation does not provide the correct instruction to perform the RH-SSO upgrade for script mappers.

It is described at

https://access.redhat.com/documentation/en-us/red_hat_single_sign-on/7.6/html-single/upgrading_guide/index#removal_of_the_literal_upload_scripts_literal_feature

__2.1.3. Removal of the upload-scripts feature
Previous versions of Red Hat Single Sign-On had supported managing JavaScript code through the management interfaces like the administrations console and REST API. Starting from this version this is no longer possible, and you should now deploy your scripts to the server in order to configure the following providers:

OpenID Connect Script Mapper
Script Authenticator (Authentication Execution)
JavaScript Policies
More details about how to deploy scripts to the server are available in the documentation. Note that to use scripts, you are still required to enable the scripts technology preview feature.

./standalone.sh -Dkeycloak.profile=preview
When deploying scripts, the server is going to automatically create their corresponding providers so that you can select them when configuring authentication flows, mappers, and authorization policies.

In general, the steps to update your realms are the following:

Before upgrading, remove any script provider you are using.
After the upgrade, deploy your scripts following the instructions in the documentation.
Update your authentication flows, mappers, and the client authorization settings to use the providers created from the scripts deployed to the server._
_

When it is referring to the documentation, the documentation link is referring to KC 21
at

https://www.keycloak.org/docs/latest/server_development/#_script_providers

the main issue is that you need to build a jar file, and deploy using teh command:

_Deploy the script JAR
Once you have a JAR file with a descriptor and the scripts you want to deploy, you just need to copy the JAR to the Keycloak providers/ directory, then run bin/kc.[sh|bat] build._

kc.sh build are typical RHBK/keycloak.x instructions, which are not available with RH-SSO 7.6
Nor the providers directory only exist on RHBK/keycloak.x distribution

Requirement:
The requirement is to provide the correct instructions (and pointers link) to be able to deploy correctly this jar file file on RH-SSO 7.6