[InstrProfData] Bump the raw profile version to 8

This is to account for the change that made CountersPtr in __profd_
relative which landed in a1532ed2.
That change hasn't updated the raw profile version, and while the
profile layout stayed the same, profiles generated by tip-of-tree
LLVM are incompatible with 13.x tooling.

Differential Revision: https://reviews.llvm.org/D111123