Remove custom skins.tgz file

I have no idea what it's for. Some backup which should have never
been on the server? It includes the /skins/contrib/Wikimedia
directory from around 2010 and some CVS metadata. Kill it.

Bug: 54823
Change-Id: I37a6fa68ec77378a9f285be3c72390ffbd20225c
Merge "Remove custom skins.tgz file"