API: Document a level of 'all' in action=protect

API: Document a level of 'all' in action=protect

It should be mentioned in the documentation for the 'protections'
parameter that 'all' exists to explicitly allow everyone to use the
action.

And the example using it seems to confuse some people into illogically
thinking that "action=all" means "restrict from all" rather than
"restrict to all" even though every other possible value means
"restrict to X", so reiterate it there too.

Bug: T141367
Change-Id: I2c3a2bf193c2ccb1ed28991ac785f7fee4948e6a