Update url for csharp (#874)

Author: jordan-smith721

snooty.toml

@@ -12,18 +12,5 @@ stable-api = "Stable API"
 node-driver-long = "MongoDB Node.js Driver"
 node-driver-short = "Node.js Driver"
 
-csharp-version = "2.18"
-csharp-docs-versioned = "https://mongodb.github.io/mongo-csharp-driver/{+csharp-version+}"
-
 java-version = "4.9"
 java-api = "https://mongodb.github.io/mongo-java-driver/{+java-version+}"
-
-[[banners]]
-targets = ["csharp.txt"]
-
-variant = "tip"
-value = """ \
-    A new version of the .Net/C# driver documentation is now live. To learn more about using \
-    the driver in your application, see the `official MongoDB C# driver documentation \
-    <https://www.mongodb.com/docs/drivers/csharp/current/>`__.
-    """