fix: x86-64 Darwin CI; remove left-over FIXMEs

[michalrus]

Context

Currently on main, the x86_64-darwin run is failing:

Initialized empty Git repository in /private/tmp/nix-build-treefmt-check.drv-0/project/.git/
treefmt v2.1.02024/11/29 13:49:41 INFO using config file: /nix/store/vpf1yg6dcq9765d0qbq94mbq32kipgzw-treefmt.toml
Error: failed to create composite formatter: failed to initialise formatter yamlfmt: formatter command not found in PATH

I was able to reproduce locally, but didn't investigate why. Probably not worth the time, considering we're running 2 other yamlfmts – on x86_64-linux and aarch64-darwin, and they work there.

IMO, let's just disable yamlfmt on x86_64-darwin, and call it a day.

I also removed 2 FIXMEs that I missed in #93 – sorry! 🫣

Important Changes Introduced

none

[michalrus]

@gytis-ivaskevicius, or maybe making the formatter work there would be a task you'd like? I don't know if you have a Darwin machine, though.