Update version number in llvm python bindings

Summary:
The version number has come out of sync with what is in CMakeLists.txt,
causing loading the bindings to fail.

Reviewers: AustinWells, abhina.sree

Reviewed By: AustinWells

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69436