license: "Red Hat, Inc." agreement in RELICENSE.md

A large part of the copyright on NetworkManager belongs to Red Hat, Inc.
I talked with legal team (Scott Peterson), and they agree with the
relicensing of NetworkManager code under LGPL-2.1+ code.

On Red Hat's behalf, I hereby mark the agreement to the license change.

RELICENSE.md

@@ -87,4 +87,4 @@ The contributors above may have contributed the code on behalf of a company
 that holds the copyright. This list tracks such legal entities. The contributor
 list above indicates whether a contributor provided code for a legal entity here.
 
-- [?] Red Hat, Inc.
+- [Y] Red Hat, Inc.