Removed non-existent labs file export
Removed non-existent labs file export

refs https://github.com/TryGhost/Ghost/commit/9e2b21578aebe4785a0a11efe444038c60bf8aea

Since the ref'd commit the labs middleware was moved to the shared labs module
and this require path no longer exists. This does not break anything as any module
still using this would error when reading the labs property
janvt/Ghost,TryGhost/Ghost,TryGhost/Ghost,ErisDS/Ghost,ErisDS/Ghost,ErisDS/Ghost,e10/Ghost,e10/Ghost,TryGhost/Ghost,janvt/Ghost