[NFC] remove unnecessary comments

src/ir/bits.h

@@ -457,7 +457,6 @@ Index getMaxBits(Expression* curr,
       return 8 * load->bytes;
     }
   } else if (auto* block = curr->dynCast<Block>()) {
-    // TODO: getFallthrough(block, ..., ...) is needed for localset.
     if (localInfoProvider && !block->name.is() && block->list.size() > 0 &&
         block->type.isConcrete()) {
       return getMaxBits(block->list.back(), localInfoProvider);