Fix USG copyright on STIX Version 2.1 OASIS Standard

Initial description deprecated after USG agreed to modifications:

**original**
-STIX v2.1 was published without USG copyright notice as originally agreed. 

Url: [http://docs.oasis-open.org/cti/stix/v2.1/os/stix-v2.1-os.html
]
Corrections:  Republish with "Portions copyright © United States Government 2012-2021. All Rights Reserved." added to front page Notices section right after OASIS copyright.-
**end original**

Make changes per attached file : stix-v2.1-os-FORENSIC-jbc2022.docx

Changes appear to consist of removing all the STIX and TAXII TM markings, adding a bolus of USG copyright info to the Notices sections, and setting the copyright year to 2022.