Remove deprecated tutorial links (#28905)

Author: jonathanfrappier

website/content/docs/concepts/username-templating.mdx

@@ -152,7 +152,5 @@ each field. This results in `v_token-wi_my_custo_abcdefghijklmnopqrst_1234567890
 
 ## Tutorial
 
-Refer to the following tutorials for step-by-step instructions.
-
-- [Database Secrets Engine with MongoDB](/vault/tutorials/db-credentials/database-mongodb#customize-the-generated-username-schema)
-- [Dynamic Secrets: Database Secrets Engine](/vault/tutorials/db-credentials/database-secrets#define-a-username-template)
+Refer to the [Database secrets
+engine](/vault/tutorials/db-credentials/database-secrets#define-a-username-template) for step-by-step instructions.

website/content/docs/secrets/databases/mongodb.mdx

@@ -102,9 +102,8 @@ for more information.
 
 ## Tutorial
 
-Refer to [Database Secrets Engine with
-MongoDB](/vault/tutorials/db-credentials/database-mongodb) for a
-step-by-step tutorial.
+Refer to [Database Secrets Engine tutorial](/vault/tutorials/db-credentials/database-secrets) for a
+step-by-step example of using the database secrets engine.
 
 ## API