loosen ruby requirement. (#902)
loosen ruby requirement. (#902)

Note that this isn't that thredded already supports ruby 3.0,
it's just that we need to loosen the requirement in order
to release dependent gems that support ruby 3.0.
thredded/thredded,thredded/thredded,jayroh/thredded,jayroh/thredded,jayroh/thredded,thredded/thredded,jayroh/thredded,thredded/thredded