Cris 'Cyborg' Santos -- Ronda Rousey's Too Scared to Fight Me

Ronda Rousey's too chicken to fight Cris 'Cyborg' Santos ... and that's why Cyborg won't be facing Rousey in Rousey's first ever UFC fight next February -- Cyborg's rep tells TMZ.FYI -- Cyborg is widely regarded as one of the most dominant female…