tree-wide: drop copyright headers from frequent contributors

Fixes #9320.

for p in Shapovalov Chevalier Rozhkov Sievers Mack Herrmann Schmidt Rudenberg Sahani Landden Andersen Watanabe; do
  git grep -e 'Copyright.*'$p -l|xargs perl -i -0pe 's|/([*][*])?[*]\s+([*#]\s+)?Copyright[^\n]*'$p'[^\n]*\s*[*]([*][*])?/\n*|\n|gms; s|\s+([*#]\s+)?Copyright[^\n]*'$p'[^\n]*\n*|\n|gms'
done

src/network/netdev/netdevsim.c

@@ -1,7 +1,4 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
-/***
-  Copyright © 2018 Susant Sahani
-***/
 
 #include "netdev/netdevsim.h"
 #include "missing.h"