Relicense GPL-2.0-only test files to GPL-2.0-or-later

All contributors are recorded in relicensecheck.pl
2 jobs for master in 29 minutes and 20 seconds (queued for 23 minutes and 12 seconds)
Status Job ID Name Coverage
  Build
passed #67078
build_clazy_clang_tidy

00:12:23

passed #67077
linux kf5-qt5 qt5.12

00:16:56

45.0%