Bump nginx minor version
Bump nginx minor version

We need to do this for two (probably related) reasons:

Puppet is failing to run on all machines that have nginx because we pin
the verison "1.4.6-1ubuntu3.4" which is now unavailable:

```
lauramartin@integration-backend-1:~$ sudo apt-cache madison nginx |grep
"1.4.6-1ubuntu3.4"
lauramartin@integration-backend-1:~$
```

There has also been a vulnerability flagged by Ubuntu for that specific
version of nginx which has been patched in the next minor version
(1.4.6-1ubuntu3.5).

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet