Revert D29647586: [jit] Renamed prim::Concat as prim::VarConcat
Test Plan: revert-hammer
Differential Revision:
D29647586 (https://github.com/pytorch/pytorch/commit/db11619901e1bd941042af4c49c6e9da7b0d206d)
Original commit changeset: cdd34ea5a3c9
fbshipit-source-id: bab5ac4ed67a00ac151fe39463aa3fb56897d7f4
