* migrate pallet-randomness-collective-flip to pallet attribute macro

Signed-off-by: koushiro <[email protected]>

* fix some nits

Signed-off-by: koushiro <[email protected]>

* remove some spacing things

Signed-off-by: koushiro <[email protected]>

* remove space

Signed-off-by: koushiro <[email protected]>

* use tabs

Signed-off-by: koushiro <[email protected]>