selftests: drv-net: add missing trailing backslash

Commit b3ea4164 ("testing: net-drv: add basic shaper test")
removed the trailing backslash from the last entry. We have
a terminating comment here to avoid having to modify the last
line when adding at the end.

Reviewed-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20241010211857.2193076-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>