(DOCSP-30846) Adds deprecation banner to legacy docs (#822) (#824)

* (DOCSP-30846) Adds deprecation banner to legacy docs

* Fixes link

Author: sarahsimpers

snooty.toml

@@ -241,3 +241,10 @@ tls = ":abbr:`TLS (Transport Layer Security)`"
 url = ":abbr:`URL (Uniform Resource Locator)`"
 utc = ":abbr:`UTC (Coordinated Universal Time)`"
 vpc = ":abbr:`VPC (Virtual Private Cloud)`"
+
+[[banners]]
+targets = ["*"]
+variant = "info"
+value = """\
+    This version of the documentation is archived and no longer supported. View the `current documentation <https://www.mongodb.com/docs/mongocli/stable/>`__ to learn how to `upgrade your version of MongoCLI <https://www.mongodb.com/docs/mongocli/stable/install/#update-the-mongodb-cli>`__.\
+    """