Revert "Merge pull request #620 from alphagov/valtech_ip"
Revert "Merge pull request #620 from alphagov/valtech_ip"

We did the user testing in Valtech on Dec 2nd 2016. Now we can remove
they whitelisted IP 51.179.154.252.

This reverts commit cd15b7e91dd91bbd0e82ec32d3d756a35efaa3f6, reversing
changes made to a73dc31d3e2bfcd9aa14c8722c75595d3b11da16.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf