Unpin PasteDeploy dependency version

Fixes bug #1133262

There are no newer releases of PasteDeploy than 1.5.0 and we have no
reason to believe newer versions will break us. Indeed, if an
incompatible version is released, we will want to know about it quickly.

Change-Id: I331b33b16ea50202886b19bf5c4060d9fa46d5ec