Remove middleware function that is never called (#13642)
Remove middleware function that is never called (#13642)

Follow-up to #12218, missed this bit of code.
flybayer/next.js,zeit/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,azukaru/next.js,flybayer/next.js,flybayer/next.js,azukaru/next.js,flybayer/next.js,JeromeFitz/next.js,azukaru/next.js,azukaru/next.js,zeit/next.js,JeromeFitz/next.js