bump download- and upload-artifact to v4 #2076

Job	Run time
Docs - stable toolchain (recent)	32s
Lint - nightly toolchain (recent)	41s
Test - nightly toolchain (minimal)	14m 21s
Test - nightly toolchain (recent)	14m 3s
Test - stable toolchain (minimal)	16m 10s
Test - 1.63.0 toolchain (minimal)	25m 37s
Test - stable toolchain (recent)	16m 13s
Test - 1.63.0 toolchain (recent)	25m 32s
Bench - nightly toolchain (recent)	1m 7s
Docs - nightly toolchain (recent)	29s
Embedded	1m 10s
Format - nightly toolchain	11s
Integration tests - stable toolchain (26_0)	59s
Integration tests - stable toolchain (25_2)	57s
Integration tests - stable toolchain (25_1)	54s
Integration tests - stable toolchain (25_0)	47s
Integration tests - stable toolchain (24_2)	58s
Integration tests - stable toolchain (24_1)	1m 0s
Integration tests - stable toolchain (24_0_1)	58s
Integration tests - stable toolchain (23_2)	58s
Integration tests - stable toolchain (23_1)	54s
Integration tests - stable toolchain (23_0)	56s
Integration tests - stable toolchain (22_1)	57s
Integration tests - stable toolchain (22_0)	53s
Integration tests - stable toolchain (0_21_2)	59s
Integration tests - stable toolchain (0_20_2)	1m 4s
Integration tests - stable toolchain (0_19_1)	53s
Integration tests - stable toolchain (0_18_1)	56s
Integration tests - stable toolchain (0_17_1)	56s
	2h 12m 5s

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