Fix setting launch position in the Settings UI not working (#14518)

## Summary of the Pull Request
This change should have been a part of #14190 but was missed. 

## PR Checklist
* [x] Closes #14469 
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [x] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

## Validation Steps Performed
Setting launch position in the settings UI works now

src/cascadia/TerminalSettingsEditor/LaunchViewModel.cpp

@@ -68,7 +68,7 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
         const auto x = _Settings.GlobalSettings().InitialPosition().X;
         // If there's no value here, return NAN - XAML will ignore it and
         // put the placeholder text in the box instead
-        const auto xCoord = x.try_as<int64_t>();
+        const auto xCoord = x.try_as<int32_t>();
         return xCoord.has_value() ? gsl::narrow_cast<double>(xCoord.value()) : NAN;
     }
 
@@ -77,7 +77,7 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
         const auto y = _Settings.GlobalSettings().InitialPosition().Y;
         // If there's no value here, return NAN - XAML will ignore it and
         // put the placeholder text in the box instead
-        const auto yCoord = y.try_as<int64_t>();
+        const auto yCoord = y.try_as<int32_t>();
         return yCoord.has_value() ? gsl::narrow_cast<double>(yCoord.value()) : NAN;
     }