fix: patch rust version to 1.81 as of 2025-01-01 #616

Job	Run time
nix-fmt-check	22s
nix-build (fuel, ubuntu-latest)	9s
nix-build-book	26s
nix-build (fuel, macos-latest)	37s
nix-build (fuel, macos-latest-xlarge)	40s
nix-build (fuel-beta-4, ubuntu-latest)	8s
nix-build (fuel-beta-4, macos-latest)	39s
nix-build (fuel-beta-4, macos-latest-xlarge)	41s
nix-build (fuel-beta-5, ubuntu-latest)	9s
nix-build (fuel-beta-5, macos-latest)	37s
nix-build (fuel-beta-5, macos-latest-xlarge)	41s
nix-build (fuel-testnet, ubuntu-latest)	9s
nix-build (fuel-testnet, macos-latest)	38s
nix-build (fuel-testnet, macos-latest-xlarge)	40s
nix-build (fuel-ignition, ubuntu-latest)	13s
nix-build (fuel-ignition, macos-latest)	40s
nix-build (fuel-ignition, macos-latest-xlarge)	40s
nix-build (fuel-mainnet, ubuntu-latest)	10s
nix-build (fuel-mainnet, macos-latest)	42s
nix-build (fuel-mainnet, macos-latest-xlarge)	40s
nix-build (fuel-nightly, ubuntu-latest)	12s
nix-build (fuel-nightly, macos-latest)	39s
nix-build (fuel-nightly, macos-latest-xlarge)	41s
nix-build (sway-vim, ubuntu-latest)	9s
nix-build (sway-vim, macos-latest)	38s
nix-build (sway-vim, macos-latest-xlarge)	40s
nix-develop (ubuntu-latest)	1m 18s
nix-develop (macos-latest)	1m 33s
nix-develop (macos-latest-xlarge)	1m 33s
notify-slack-on-failure	0s
	17m 4s

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