doc/lxd-to-incus: Add mention of group changes #601

Job	Run time
Documentation	7m 5s
Code	6m 10s
Client (1.20.x, ubuntu-latest)	1m 3s
Client (1.20.x, macos-latest)	1m 51s
Client (1.20.x, windows-latest)	2m 43s
System (1.20.x, cluster, dir)	12m 7s
System (1.20.x, cluster, btrfs)	12m 13s
System (1.20.x, cluster, lvm)	12m 55s
System (1.20.x, cluster, zfs)	13m 17s
System (1.20.x, cluster, ceph)	17m 31s
System (1.20.x, cluster, random)	12m 31s
System (1.20.x, standalone, dir)	22m 49s
System (1.20.x, standalone, btrfs)	22m 2s
System (1.20.x, standalone, lvm)	41m 6s
System (1.20.x, standalone, zfs)	43m 20s
System (1.20.x, standalone, ceph)	1h 12m 54s
System (1.20.x, standalone, random)	23m 8s
System (stable, cluster, dir)	12m 49s
System (stable, standalone, dir)	21m 32s
System (tip, cluster, dir)	13m 31s
System (tip, standalone, dir)	22m 26s
	6h 35m 3s

Provide feedback