Have the conceal flow call updateChapter as well.

[johndoknjas]

This'd be useful for something I'm working on with edit chapter atm.

Only functional change of this PR should be that if a user (un)sets the "Hide next moves" mode, they'll be marked as active.

[ornicar]

Considering that this doesn't fix an existing bug, doesn't simplify the code, and has the potential of adding new bugs, I'm not too inclined to merge. Am I missing something?

[johndoknjas]

@ornicar A few small benefits imo:

• Gives the active flash for a user when they toggle hide mode.
• With all cases now calling updateChapter if a reload should be done, it's a bit simpler. Also helps if we ever want to modify the frontend behaviour for when the user submits an edit change, since now the only entrypoint is the updateChapter socket.