Windows state deprecations

I noticed some deprecated properties in [`ISerializedWindowState`](https://github.com/microsoft/vscode/blob/d8a4891005347b287fca620f2f20243e063f5807/src/vs/platform/windows/electron-main/windowsStateStorage.ts#L25) from https://github.com/microsoft/vscode/commit/a221cdd12b866be90aa987cc5df3b7d1f71fc18d it seems. I think by now we can probably clean that up. 