doc/user: update the udev rule to handle bind/unbind events
Summary: we expect add, change or remove but kernel 4.12 added bind and unbind. These events were previously discarded by udevd. Our rules should handle any event but remove, so update as suggested in the announce email linked below.
For a longer explanation, see the system 247rc2 announcement https://lists.freedesktop.org/archives/systemd-devel/2020-November/045570.ht
See cd37dcfa where we did this already for the udev rules we use ourselves.
Triggered by #904 (comment 1956162)