browser: avoid 404 errors during install

Given the openssh image already runs an apt-get update and, at this time,
I'm building this image shortly after that one, I don't see why I'm getting
a 404 error at all.

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
Merge pull request #10 from kemitix/feature/browser-fix-404-on-build

browser: avoid 404 errors during install