selftests: kselftest: Remove outdated comment

selftests: kselftest: Remove outdated comment

BugLink: https://bugs.launchpad.net/bugs/1812198
Commit 3c07aaef6598 ("selftests: kselftest: change KSFT_SKIP=4 instead of
KSFT_PASS") reverted commit 11867a77eb85 ("selftests: kselftest framework:
change skip exit code to 0") but missed removing the comment which that
commit added, so do that now.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
(cherry picked from commit c31d02d1290e1e82a08015199e408228e152991f)
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>