[NFC] Fix typo in Inlining (#6187)

Author: kripken

src/passes/Inlining.cpp

@@ -765,8 +765,8 @@ struct FunctionSplitter {
  return InliningMode::Uninlineable;
  }
  } else {
- // This is an if without an else, and so the type is either none of
- // unreachable;
+ // This is an if without an else, and so the type is either none or
+ // unreachable, and we ruled out none before.
  assert(iff->ifTrue->type == Type::unreachable);
  }
  }