[InstCombine] Remove some code from visitAnd that dealt with trying to reduce...

[InstCombine] Remove some code from visitAnd that dealt with trying to reduce the LHS of a sub to 0. This should now be fully handled by SimplifyDemandedInstructionBits now.

Now that we call ShrinkDemandedConstant on the RHS of sub this should be taken care of. This code doesn't trigger on any in tree regressions, but did before ShrinkDemandedConstant was added to the RHS.

llvm-svn: 298644