change dapper-plus citation (#2083)

Author: mgravell

docs/dapper-sponsor.png

@@ -10,4 +10,4 @@ From 2024, Dapper Plus is now a major sponsor of Dapper, helping to secure ongoi
 This sponsorship does not impact the ownership, license, or any other particulars of how Dapper operates. The core Dapper libraries continue
 to be freely available and fully open source.
 
-<a href="https://www.learndapper.com/"><img width="728" height="90" alt="Dapper Plus logo" src="https://dapperlib.github.io/Dapper/dapper-sponsor.png" /></a>
+<a href="https://dapper-plus.net/"><img width="728" height="90" alt="Dapper Plus logo" src="https://dapperlib.github.io/Dapper/dapper-sponsor.png" /></a>

docs/dapperplus.md

@@ -25,4 +25,4 @@ A huge thanks to everyone (individuals or organisations) who have sponsored Dapp
 - [Dapper Plus](https://dapper-plus.net/) is a major sponsor and is proud to contribute to the development of Dapper ([read more](https://dapperlib.github.io/Dapper/dapperplus))
 - [AWS](https://github.com/aws) who sponsored Dapper from Oct 2023 via the [.NET on AWS Open Source Software Fund](https://github.com/aws/dotnet-foss)
 
-[![Dapper Plus logo](https://raw.githubusercontent.com/DapperLib/Dapper/main/docs/dapper-sponsor.png)](https://www.learndapper.com/)
+[![Dapper Plus logo](https://raw.githubusercontent.com/DapperLib/Dapper/main/docs/dapper-sponsor.png)](https://dapper-plus.net/)