`om ci`: flake check should be disabled by default

[srid]

devour-flake already builds the checks.

So we should disble by this default since most flakes don't have templates to check:

omnix/om.yaml

Lines 51 to 53 in 7e35ac5

	# Run `nix flake check` for checking the 'templates' outputs
	flake-check:
	enable: true