ENG-6736: Fix issue in the SAML Certificate data source

[VictorGFM]

Description of the change

The TestAccSAMLCertificateDataSource is currently failing in an environment that uses a Control Plane without any existing SSO integration. That generates a cyclic dependency while trying to use the data source in the IDP Okta module. This PR fixes the SAML Certificate data source so that the certificate can be retrieved without depending on an SSO Integration.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• Jira issue referenced in commit message and/or PR title

Testing

Tested through manual Terraform configuration and running go test -v -run=^TestAccSAMLCertificateDataSource$ using the Edge Control Plane in version v2.24.1