Remove redundant copyright, now there is a license file

Author: kaashoek

README

@@ -31,9 +31,6 @@ Rafael Ubal, Amane Uehara, Pablo Ventura, Xi Wang, WaheedHafez,
 Keiichi Watanabe, Lucas Wolf, Nicolas Wolovick, wxdao, Grant Wu, x653,
 Jindong Zhang, Icenowy Zheng, ZhUyU1997, and Zou Chang Wei.
 
-The code in the files that constitute xv6 is
-Copyright 2006-2024 Frans Kaashoek, Robert Morris, and Russ Cox.
-
 ERROR REPORTS
 
 Please send errors and suggestions to Frans Kaashoek and Robert Morris