fix: `desktopCapturer.getSources` gets app windows on Windows

[erickzhao]

Description of Change

Checklist

• [ ] PR description included and stakeholders cc'd
• [ ] npm test passes
• [ ] tests are changed or added
• [ ] relevant documentation, tutorials, templates and examples are changed or added
• [ ] PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: fixed bug where desktopCapturer.getSources() would not return the app's own BrowserWindows on Windows.