Copyright for changes in Platform TCK test sources to existing files versus new source files

https://github.com/jakartaee/platform-tck/pull/664#issuecomment-943475295 has some discussion that points to https://www.eclipse.org/lists/jakartaee-tck-dev/msg00466.html

This came up recently on https://github.com/jakartaee/platform-tck/pull/1312