Linux build: Ubuntu Software Center complains "The package is of bad quality"

[pauloppenheim]

• VSCode Version: 1.4, master
• OS Version: Ubuntu 14.04

Steps to Reproduce:

1. run gulp vscode-linux-x64-build-deb
2. open .build/linux/deb/amd64/deb/code-oss_1.5.0-1473128807_amd64.deb (or whatever your tagged build result is) in your file chooser (ie, open in Nautilus, double click)
3. Wait for Ubuntu Software Center to open and show the package
4. Warning pops up:
   

I have fixed this, it's small, but opening the bug before the PR so I can reference this.