selftests: net: Fix typo 'the the' in comment

Replace 'the the' with 'the' in the comment.

Signed-off-by: Slark Xiao <slark_xiao@163.com>
Link: https://lore.kernel.org/r/20220725020124.5760-1-slark_xiao@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>