set_versions.py: mark Styhead as EoL
Styhead is now EoL, let's remove it from the active releases.
(From yocto-docs rev: f2e3cf2637ce3ed3475faa472b134a29f019681b)
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>