Fix MonoGame.Framework.dll.config to be named properly on MacOS and Linux

The output DLLs for MacOS and Linux were [recently renamed](https://github.com/mono/MonoGame/commit/9a77339a68916dbc83b774bb0df495e58ac6fa41) to not include any suffix.

This commit updates the output names of the correspondig .dll.config files to match the new names. 

This is required for MonoGame to work at all on Mac and Linux.