fix(PeriphDrivers): Remove unused aes_me18.c

[sihyung-maxim]

Description

Related to https://github.com/Analog-Devices-MSDK/msdk/issues/773

This PR removes aes_me18.c, an unused library file that was leftover from when the MAX32690 SDK was brought up.

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• [ ] PR Title follows correct guidelines.
• [ ] Description of changes and all other relevant information.
• [ ] (Optional) Link any related GitHub issues using a keyword
• [ ] (Optional) Provide info on any relevant functional testing/validation. For API changes or significant features, this is not optional.