Update amsynth to 1.10.0

Summary: Changelog available here

Test Plan: Try controlling it with VMPK, play with knobs and check that it produces sound.

Reviewers: Triage Team, JoshStrobl

Reviewed By: Triage Team, JoshStrobl

Subscribers: JoshStrobl

Differential Revision: https://dev.getsol.us/D9357