[GlobalISel] Disable vector types in narrowScalarAddSub

The implementation for vectors is broken and doesn't seem to be used by
anything. Explicitly remove support for them, they can be added again
later when they're properly implemented.

Reviewed By: aemerson

Differential Revision: https://reviews.llvm.org/D95699

GitOrigin-RevId: 97a1cdb15618966f786404bcfcac08f52a695f55
1 file changed