doc: describe how to revert sec lockout

[sam-github]

No description provided.

[sam-github]

@richardlau WDYT, does this describe what you did? I think we both did it at the same time.

[richardlau]

The additional text LGTM (I also didn't see a way to restore the old permissions from the history view). We might need to have a discussion on what the "normal" permissions are supposed to be. I was paranoid and took a picture of the permissions prior to editing them for the lockdown. They looked as follows and you'll note there's several entries that weren't in the picture in the guide:

I did put all these back, but unfortunately it looks like because we both did it at the same time the changes I made were immediately overwritten by the ones you did (no blame there, the guide is either inaccurate or we'd somehow accrued a bunch of permissions that shouldn't have been there).

There was at least one previous attempt to update the guide which stalled out: #1450

[sam-github]

@richardlau I pushed your screenshot update into this PR

[richardlau]

Kind of wish I'd noticed before that I'd cut off the headers in the screen snip.

[sam-github]

I retook the screenshot, with all the headers.