[NFC] make clang/test/CodeGen/arm_neon_intrinsics.c resistent to function attribute id changes

When introducing support for @llvm.experimental.noalias.scope.decl, this tests started failing because it checks
(for no good reason) for a function attribute id of '#8' which now becomes '#9'

Reviewed By: pratlucas

Differential Revision: https://reviews.llvm.org/D94233