Update terms_of_use license information due to NIWC taking over management of the OVAL language

[vanderpol]

Abstract
With CIS stepping down from the OVAL sponsor, the XSD files should no longer have any CIS copyrights in them. As NIWC is part of the Navy, and the US government doesn't normally copyright files, the licenses will likely be updated without any specific copyright information. If you have any issues/suggestions on this, please leave a comment.

Link to Proposal
Once a proposal has been put into pull request form, add a link to the PR here. If and as alternate proposals or objections are added they should be linked here as well.

Additional context
Add any other context or screenshots about the enhancement.

[vanderpol]

Below is the current Terms of Use:

<terms_of_use>Copyright (c) 2016, Center for Internet Security. All rights reserved. The contents of this file are subject to the terms of the OVAL License located at https://oval.cisecurity.org/terms. See the OVAL License for the specific language governing permissions and limitations for use of this schema. When distributing copies of the OVAL Schema, this license header must be included.</terms_of_use>

I have contacted legal departments at CISA and NIWC for guidance

[vanderpol]

Merged PR into develop, closing issue