Chore/update nim version #4121

Job	Run time
coverage	17m 47s
matrix	19s
build / linux-unittest-amd64-v2.0.12	16m 53s
build / linux-contract-amd64-v2.0.12	9m 18s
build / linux-integration-amd64-v2.0.12	1h 6m 28s
build / linux-tools-amd64-v2.0.12	9m 25s
build / macos-unittest-amd64-v2.0.12	20m 24s
build / macos-contract-amd64-v2.0.12	10m 40s
build / macos-integration-amd64-v2.0.12	1h 20m 55s
build / macos-tools-amd64-v2.0.12	12m 21s
build / windows-unittest-amd64-v2.0.12	33m 3s
build / windows-contract-amd64-v2.0.12	19m 47s
build / windows-integration-amd64-v2.0.12	1h 34m 39s
build / windows-tools-amd64-v2.0.12	21m 54s
build / status	1s
	6h 53m 54s

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