Update actions/upload-artifact action to v6 #186

Job	Run time
cargo fmt	15s
cargo clippy (default+elgamal3)	23s
test wasm bindings	2m 36s
test python bindings	1m 10s
cargo clippy (default+python+elgamal3)	30s
cargo clippy (default+wasm)	35s
cargo test (default+python)	1m 8s
cargo test (default+legacy)	49s
cargo clippy (default)	18s
cargo clippy (default+wasm+elgamal3)	28s
cargo clippy (default+legacy)	19s
cargo test (default+python+elgamal3)	1m 1s
cargo test (default+wasm)	1m 9s
cargo test (default)	56s
cargo test (default+wasm+elgamal3)	1m 7s
cargo test (default+elgamal3)	50s
cargo clippy (default+python)	32s
	14m 6s

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