Change "brought to you" into "managed" in headers

Change "brought to you" into "managed" in headers

File headers are there to indicate that the files should not be touched
directly on the server. By changing the first sentence to "This file is
managed by Puppet", we reinforce the idea that it is already taken care
of by something else.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>