Update I_Acknowledgments.md for new username (#111)

Author: IAmTheNerdNextDoor

99_Appendices/I_Acknowledgments.md

@@ -22,4 +22,4 @@ In no particular order:
 - @Hqnnqh ([https://github.com/Hqnnqh](https://github.com/Hqnnqh))
 - @malletgaetan ([https://github.com/malletgaetan](https://github.com/malletgaetan))
 - @mrjbom ([https://github.com/mrjbom](https://github.com/mrjbom))
-- @AFellowSpeedrunner ([https://github.com/AFellowSpeedrunner](https://github.com/AFellowSpeedrunner))
+- @IAmTheNerdNextDoor ([https://github.com/IAmTheNerdNextDoor](https://github.com/IAmTheNerdNextDoor))