[AG] Problems with registry doc

In https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.4/html-single/administration_guide/index#devfile-registry_crw, I see a few problems:

Downstreaming

• link to https://github.com/eclipse/che-devfile-registry and https://github.com/eclipse/che-plugin-registry should be replaced with their downstream equivalents:
  • https://github.com/redhat-developer/codeready-workspaces/tree/crw-2.4-rhel-8/dependencies/che-devfile-registry
  • https://github.com/redhat-developer/codeready-workspaces/tree/crw-2.4-rhel-8/dependencies/che-plugin-registry
• container images are wrong too, they should be:
  • registry.redhat.io/codeready-workspaces/devfileregistry-rhel8:2.4
  • registry.redhat.io/codeready-workspaces/pluginregistry-rhel8:2.4

• Inconsistencies

• Section 1.1.3 is titled "1.1.3. Devfile registry", but section 1.1.4 is titled "1.1.4. CodeReady Workspaces plug-in registry". The simpler title for "1.1.4 Plug-in registry" seems more appropriate to me, but then it'll be inconsistent with sections 1.1.1 through 1.1.6. Perhaps you want to simplify all those section titles, and the 1.2.x titles too?

• text under devfile section 1.1.3 says "For more information about devfile registry customization, see the Customizing devfile registry section." with no link. It should link to https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.4/html-single/administration_guide/index#building-a-custom-devfile-registry_crw