Fix some iffy grammar in the NOTICE file.
Fix some iffy grammar in the NOTICE file.

Incorporated from https://github.com/znc/znc/pull/939

This fixes some minor nitpicks including:
- Code is licensed under a license, not by a license.
- The public domain is not a license.

Kriechi/nobnc,Kriechi/nobnc,Kriechi/nobnc