metrics: remove broken dependency on Apache site

since Id10e7b844ac1 we are using the new apache::site
to setup the Apache site, but that means we write
sites into sites-available and symlink to sites-enabled,
as we should

that breaks this dependency, and i argue that the logfiles
being readable for that group does not even really require
that Apache site to exist.

if you should disagree with the last part, please tell me what it
should depend on now

Change-Id: I38c2c1db4618fd090bfb8670bf314968bc296c03