fix(home-manager/gtk): replace `normal` tweak with `default`

[isabelroses]

Seeing as this does not exist and should be default we should remove the "normal" and replace it with default

[jpotier]

I'm quite confused as I'm facing the opposite problem now: default doesn't exist, but normal does…

[jpotier]

This makes no sense:

Upstream https://github.com/catppuccin/gtk/releases clearly has "default" suffix.

[isabelroses]

Yeahhhh... we had this exact same problem right after fixing it too. The issue is I keep getting weird builds with default and others with normal. I think we should just revert this @getchoo .