flexVDI: desktop file does not pass desktop-file-validate

```
/tmp/.mount_appimajHe3OD/flexvdi-client.desktop: error: file contains key "Value" in group "Desktop Entry", but keys extending the format should start with "X-"

/tmp/.mount_appimajHe3OD/flexvdi-client.desktop: error: value "Network" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
```

https://travis-ci.org/AppImage/AppImageHub/builds/266118880#L541-L542

Would they a GitHub project for the FlexVDI desktop, I would have reported or even immediately fixed the issue. But since they haven't, I haven't. It's a pain to sign in somewhere else just to make a contribution like this.