[landing] fix comm copyright text

Summary:
resolves the following copyright text touchup:

https://linear.app/comm/issue/ENG-4621/c-2023-comm-all-rights-reserved

Test Plan:
Please see the screenshot

Reviewers: atul, kamil, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8781