Update broken WSO2 Store link in User Managed Access (UMA 2.0) documentation

[NilukaSripalim]

The User Managed Access (UMA 2.0) documentation contains the following instruction:

You can download the connector and other required artifacts from the WSO2 store.

The linked WSO2 Store URL currently returns a 404 Not Found response instead of the expected download page.

Current behavior:

The WSO2 Store link redirects to:

{
  "description": "The requested resource is not available.",
  "code": "404",
  "message": "Not Found"
}

Users are unable to download the required connector and artifacts by following the documentation.

Expected behavior:

The documentation should link to a valid location where users can download the required connector and artifacts.
If the WSO2 Store is no longer used, the documentation should be updated to reference the current download location.