Remove file declaration for concat-managed files

When using multiple `logcheck::logfile` defines, the following error gets thrown by puppet:

```err: Could not retrieve catalog from remote server: Error 400 on SERVER: Duplicate declaration: File[/etc/logcheck/logcheck.logfiles] is already declared in file /etc/puppet/modules/concat/manifests/init.pp at line 154; cannot redeclare on node real.jaggi.info```

This is fixed by removing the `file` declaration for `"/etc/logcheck/logcheck.logfiles"` from the `logcheck::logfile` define (the `/etc/logcheck/logcheck.logfiles` file is properly declared by concat already).