scripts/tags.sh: Update comment (addition of gtags)

Commit f4ed1009 ("kbuild: add GNU GLOBAL tags generation") added
support for the GNU Global source tagging system. However, this addition
was not reflected in the script's header comment.

Fixes: f4ed1009 ("kbuild: add GNU GLOBAL tags generation")
Signed-off-by: René Nyffenegger <mail@renenyffenegger.ch>
Link: https://lore.kernel.org/r/20231217082719.4747-1-mail@renenyffenegger.ch


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>