[watsonx-self-managed-ocp] Add prereqs to the `long_description` of DA

[ocofaigh]

Add prereqs to the long_description in the ibm_catalog.json:

GPU worker nodes that meet IBM Cloud Pak for Data requirements for watsonx software.
OpenShift Data Foundation installed. This can be installed via the module
OpenShift AI in Red Hat OpenShift installed.
Cloud Pak for Data entitlement key.

Link to relevant official docs where applicable.

[argeiger]

Those 4 pre-reqs are what should be documented. Here they are with the links for the info -

1. Red Hat OpenShift on IBM Cloud version 4.18 or higher
2. Cloud Pak for Data entitlement key
3. GPU worker nodes that meet IBM Cloud Pak for Data requirements for watsonx software
4. OpenShift AI in Red Hat OpenShift installed
5. OpenShift Data Foundation installed. You can install this via the deployable architecture

[ocofaigh]

PR: #55