Don't build beta-1 and beta-2 on CI #298

Job	Run time
nix-build-book	27s
nix-fmt-check	21s
nix-build (fuel, ubuntu-latest)	41s
nix-build (fuel, macos-latest)	2m 37s
nix-build (fuel, macos-arm)	27s
nix-build (fuel-beta-3, ubuntu-latest)	33s
nix-build (fuel-beta-3, macos-latest)	1m 59s
nix-build (fuel-beta-3, macos-arm)	17s
nix-build (fuel-beta-4, ubuntu-latest)	32s
nix-build (fuel-beta-4, macos-latest)	1m 56s
nix-build (fuel-beta-4, macos-arm)	37s
nix-build (fuel-nightly, ubuntu-latest)	43s
nix-build (fuel-nightly, macos-latest)	2m 34s
nix-build (fuel-nightly, macos-arm)	17s
nix-build (sway-vim, ubuntu-latest)	19s
nix-build (sway-vim, macos-latest)	1m 22s
nix-build (sway-vim, macos-arm)	17s
nix-develop (ubuntu-latest)	2m 19s
nix-develop (macos-latest)	4m 52s
nix-develop (macos-arm)	21s
	23m 31s

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