Remove unused (and broken) labs config from squid manifest

Per <https://bugzilla.wikimedia.org/show_bug.cgi?id=38524#c2>, squid.pp is not
applied on labs -- which is what I'd expect, given that it references an
undefined function. So: clean it up.

Bug: 38524

Change-Id: I132fef92c4870e0f2a40fa3819f53cf8fcfb4d08