Makefile: Switch to raft fork #29

Job	Run time
Code tests	10m 32s
Documentation tests	10m 52s
Client tests (1.18.x, ubuntu-latest)	1m 23s
Client tests (1.18.x, macos-latest)	1m 15s
Client tests (1.18.x, windows-latest)	2m 50s
System tests (1.18.x, cluster, dir)	15m 36s
System tests (1.18.x, cluster, btrfs)	13m 24s
System tests (1.18.x, cluster, lvm)	14m 2s
System tests (1.18.x, cluster, zfs)	14m 14s
System tests (1.18.x, cluster, ceph)	19m 40s
System tests (1.18.x, cluster, random)	14m 41s
System tests (1.18.x, standalone, dir)	22m 40s
System tests (1.18.x, standalone, btrfs)	21m 48s
System tests (1.18.x, standalone, lvm)	42m 31s
System tests (1.18.x, standalone, zfs)	42m 15s
System tests (1.18.x, standalone, ceph)	1h 10m 34s
System tests (1.18.x, standalone, random)	39m 51s
System tests (stable, cluster, dir)	14m 13s
System tests (stable, standalone, dir)	22m 14s
System tests (tip, cluster, dir)	12m 49s
System tests (tip, standalone, dir)	22m 6s
	7h 9m 30s

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