ci: update rust to 1.81 #1420

Job	Run time
tests (vmm/sandbox, --all-features)	3m 40s
checks (vmm/sandbox, --all-features)	1m 54s
tests (vmm/task, --all-features)	3m 12s
checks (vmm/task, --all-features)	1m 38s
tests (shim, --all-features)	2m 27s
checks (shim, --all-features)	1m 53s
tests (quark, --all-features)	2m 28s
checks (quark, --all-features)	1m 54s
tests (runc, --all-features)	2m 59s
checks (runc, --all-features)	1m 41s
tests (wasm, --features=wasmedge, 0.13.5)	3m 12s
checks (wasm, --features=wasmedge, 0.13.5)	1m 54s
tests (wasm, --features=wasmtime)	3m 42s
checks (wasm, --features="wasmedge, wasmedge_wasi_nn", 0.13.5)	1m 50s
checks (wasm, --features=wasmtime)	1m 50s
	36m 14s

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