Delete bad AppDb example from documentation.

It doesn't add any useful functionality, and might encourage people to use it (incorrectly) as a singleton.

Author: bgrainger

docs/content/overview/configuration.md

@@ -1,5 +1,5 @@
 ---
-lastmod: 2016-10-16
+lastmod: 2021-09-21
 date: 2016-10-16
 menu:
   main:
@@ -17,51 +17,4 @@ To connect to a database on `localhost` port `3306` with a user `mysqltest`, pas
 
 `host=127.0.0.1;port=3306;user id=mysqltest;password=Password123;database=mysqldb;`
 
-For all connection string options, view the [Connection Options Reference](/connection-options/)
-
-### Application Database Object Example
-
-It's a good idea to use an IDisposable object that configures the connection string globally, and closes the connection automatically:
-
-```csharp
-public class AppDb : IDisposable
-{
-    public readonly MySqlConnection Connection;
-
-    public AppDb()
-    {
-        Connection = new MySqlConnection("host=127.0.0.1;port=3306;user id=mysqltest;password=Password123;database=mysqldb;");
-    }
-
-    public void Dispose()
-    {
-        Connection.Close();
-    }
-}
-
-```
-
-Callers can use the Application Database Object object like so:
-
-```csharp
-public async Task AsyncMethod()
-{
-    using (var db = new AppDb())
-    {
-        await db.Connection.OpenAsync();
-        // db.Connection is open and ready to use
-    }
-    // db.Connection was closed by AppDb.Dispose
-}
-
-public void SyncMethod()
-{
-    using (var db = new AppDb())
-    {
-        db.Connection.Open();
-        // db.Connection is open and ready to use
-    }
-    // db.Connection was closed by AppDb.Dispose
-}
-
-```
+For all connection string options, view the [Connection Options Reference](/connection-options/).