doc: Contributing Guidelines Updates (#2494)

* Contributing Guidelines Updates

* Update README.md

* Update README.md

* Update contributing/README.md

Co-authored-by: kyuan-mongodb <78768401+kyuan-mongodb@users.noreply.github.com>

---------

Co-authored-by: kyuan-mongodb <78768401+kyuan-mongodb@users.noreply.github.com>

contributing/README.md

@@ -1,6 +1,6 @@
 # Contribution guidelines
 
-Thanks for your interest in contributing to MongoDB Atlas Terraform Provider, the following documents define guidelines necessary to participate in the community.
+Thanks for your interest in contributing to MongoDB Atlas Terraform Provider, the following documents define guidelines necessary to participate in the community. Please note that we no longer develop or maintain any resources or data sources we marked as deprecated in our [documentation](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs). 
 
 - [Development Setup](development-setup.md)
 - [Development Best Practices](development-best-practices.md)