Remove set_uk_apt_sources from bootstrap-vagrant

This has no effect on the baseboxes that are in use because they point to
the generic `archive.ubuntu.com` hostname instead of `us.archive`. This
already does some reasonable guesses at geo-location, so should be
sufficient.
Run `apt-get update` before installing Ruby

This was previously done on every run until `set_uk_apt_sources()` was
refactored and then removed. Not calling it results in the following the
very first time a brand new VM is brought up:
```
[bootstrap] --> Set root profile to quieten sudo tty message
[bootstrap] --> Set nameserver to 8.8.8.8 and domain to internal
[bootstrap] --> Check for Ruby
[bootstrap] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/liby/libyaml/libyaml-0-2_0.1.4-2ubuntu0.12.04.1_amd64.deb  404  Not Found [IP: 91.189.88.149 80]
[bootstrap] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
```