Meta: Fix wonky copyright headers in Tests

Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/c8668e9b7c1
Pull-request: https://github.com/SerenityOS/serenity/pull/3403

Meta/check-style.sh

@@ -39,7 +39,6 @@ while IFS= read -r f; do
 done < <(git ls-files -- \
     '*.cpp' \
     '*.h' \
-    ':!:Tests' \
     ':!:Base' \
     ':!:Kernel/FileSystem/ext2_fs.h' \
     ':!:Libraries/LibC/getopt.cpp' \

Userland/Tests/Kernel/kill-pidtid-confusion.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ * Copyright (c) 2020, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without

Userland/Tests/Kernel/setpgid-across-sessions-without-leader.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ * Copyright (c) 2020, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without