Add back reference from constraints to flags

[philderbeast]

I saw that flags referenced constraints but not vice-versa in the docs so I added the back reference.

• Patches conform to the coding conventions.

[andreabedini]

Thank you @philderbeast

[philderbeast]

@andreabedini, is it now OK to hit the green [Merge pull request] button?

[ulysses4ever]

@philderbeast we don't merge manually, generally. The bot will take care of it after a mandatory two-days delay.

Thank you for your contribution, as usual!

[philderbeast]

Thanks @ulysses4ever. We've had trouble with automated merging of my contributions before and I was wondering if we still need to watch out for this and do it manually, #9043 (comment).

[ulysses4ever]

@philderbeast oh, right, thank you for the reminder! Since then, I did implement something that should allow us to use the bot anyways (#9108). It just needs another label: not the standard merge me/merge+squath, but rather merge+no rebase. Let's try it!

The two-days-of-silence delay will automagically be honored this way, presumably.

[ulysses4ever]

And it worked — hooray!