help complete: mention remove all AND restore all

[積丹尼 Dan Jacobson]

$ help complete

      -r        remove a completion specification for each NAME, or, if no
                NAMEs are supplied, all completion specifications

Add
                To later restore them do ...

as one often wants to remove them all, try something, and then put them
all back.

I am not asking for help. I am saying $ help complete should mention
more things.