Replace quote approval policy value "No one" with "Just me"

The quote approval policies defined by "Mastodon" are: "Anyone",
"Followers only" and "Just me".
Fedilab uses "No one" instead of "Just me" which triggered #1298
This commit replaces all occurrences of "no one"/"no_one" with "Just
me"/"just_me" to match the official value.