chore: deprecation message

## Description <!-- >Thank you for your contribution ! > Please include a summary of the change and which issue is fixed. > Please also include the context. > List any dependencies that are required for this change. Fixes #123 Closes #456 --> ## Type of Change <!-- Use the check-boxes [x] on the options that are relevant. --> - [ ] Non-module change (e.g. CI/CD, documentation, etc.) - [ ] Azure Verified Module updates: - [ ] Bugfix containing backwards compatible bug fixes - [ ] Someone has opened a bug report issue, and I have included "Closes #{bug_report_issue_number}" in the PR description. - [ ] The bug was found by the module author, and no one has opened an issue to report it yet. - [ ] Feature update backwards compatible feature updates. - [ ] Breaking changes. - [ ] Update to documentation # Checklist - [ ] I'm sure there are no other open Pull Requests for the same update/change - [ ] My corresponding pipelines / checks run clean and green without any errors or warnings - [ ] I did run all [pre-commit](https://azure.github.io/Azure-Verified-Modules/contributing/terraform/terraform-contribution-flow/#5-run-pre-commit-checks) checks <!-- Please keep up to date with the contribution guide at https://aka.ms/avm/contribute/terraform -->