[CI] bump artifact actions to v4 #842

Job	Run time
Build Runtimes (encointer-node-notee)	5m 3s
build-try-runtime-and-benchmarks	4m 12s
Cancel Previous Runs	2s
build	4m 29s
cargo-toml-fmt	10s
Rust check +nightly fmt --all -- --check (x86_64-unknown-linux-gnu)	49s
unit-tests	2m 32s
Rust check clippy -p encointer-client-notee (x86_64-unknown-linux-gnu)	2m 41s
test_bootstrap_demo_community.sh	21m 28s
test_bot_community.sh	8m 57s
test_register_business.sh	2m 3s
Draft Release	0s
Publish Runtimes	0s
	52m 26s

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