[chore] Change "M1" references to "ARM-based Mac(s)"

Summary: Minor change — changed all occurrences of "M1" (not in code, in comments and documentation) to "ARM-based Mac(s)". This is because now that M2 exists, M1 only classifies the the first generation of Apple silicon Macs.

Test Plan: N/A, these were all comments and documentation so these changes are all only cosmetic.

Reviewers: atul, ashoat

Reviewed By: ashoat

Subscribers: marcinwasowicz, ashoat, palys-swm, Adrian

Differential Revision: https://phab.comm.dev/D4244