There was a typo in the code path that removes unnecessary
materializations.
Before: Update `opResult` (result of an op different from `user`) in
mapping and remove `user`.
```
replaceMaterialization(rewriterImpl, opResult, inputOperands,
inverseMapping);
necessaryMaterializations.remove(materializationOps.lookup(user));
```
After: Update `user->getResults()` in mapping and remove `user`.
```
replaceMaterialization(rewriterImpl, user->getResults(), inputOperands,
inverseMapping);
necessaryMaterializations.remove(materializationOps.lookup(user));
```
cb7614e839