deprecation banner for MEKO (#2128) (#2141)

* deprecation banner for MEKO

* tech review

(cherry picked from commit 9dc7358)

Author: jwilliams-mongo

snooty.toml

@@ -238,5 +238,8 @@ vpc = ":abbr:`VPC (Virtual Private Cloud)`"
 yaml = ":abbr:`YAML (Yet Another Markup Language)`"
 
 [[banners]]
-# dark mode/appearance in public preview
-targets = []
+targets = ["*"]
+variant = "warning"
+value = """\
+        The MongoDB Enterprise Kubernetes Operator is deprecated. There will be no future releases. Each version will reach end of life according to the :ref:`support policy <k8s-support-lifecycle>`. All of its features are available in the `MongoDB Controllers for Kubernetes Operator <https://www.mongodb.com/docs/kubernetes/>`__. Please migrate to the Controllers for Kubernetes Operator for continued support.
+        """