Docs: correct description of m19 feedback requirements
Docs: correct description of m19 feedback requirements

Signed-off-by: John <0857133ffcd232122dc51ad55bf5fcc9d60af5d3@gnipsel.com>

ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror