The first domino of the spring transfer portal window fell for Oklahoma on Tuesday. Shane Whitter announced on social media that he’ll enter the transfer portal. The redshirt senior linebacker will have two years of eligibility remaining. “First and foremost, thank you God for guiding me to where I am today,” Whitter wrote. “I would like to thank Sooner nation for an unforgettable chapter at Oklahoma! It has been an honor to work alongside the exceptional coaches, teammates and staff her who have helped me grow as a person and athlete. I am honored to have been able to call…