Removes zuul/layout-dev.yaml

The file zuul/layout-dev.yaml was moved to the project-config repo.
This copy of the file in config should have been deleted with the
others in commit 1e7874e1eb0c15adc06d0bd10da5a90a26901309 and it
wasn't. There have been no updates to this file since August 5,
2014. This patch deletes zuul/layout-dev.yaml.

Change-Id: I4d6729d289b00b3ce05aa98f27d275b5093b9f00
Merge "Removes zuul/layout-dev.yaml"