message: Fix the grammar in a comment
  ## Summary of the Pull Request
  After 'must', the verb is used without 'to'. Correct: "must" or "have to".
  ## PR Checklist
  * [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
  ## Validation Steps Performed
  Not required, only comment has been changed.
diff: @@ -1221,7 +1221,7 @@ using Microsoft::Console::VirtualTerminal::StateMachine;
  wstr.resize((dbcsLength + mbPtrLength) / sizeof(wchar_t));
  }
  - // Hold the specific version of the waiter locally so we can tinker with it if we must to store additional context.
  + // Hold the specific version of the waiter locally so we can tinker with it if we have to store additional context.
  std::unique_ptr<WriteData> writeDataWaiter{};
  // Make the W version of the call
  