This reverts commit 3452eecbcc.
The test checks that the mounts of a destroyed mount namespace stay
connected. The commit that made them stay connected is reverted next
because it leaks superblocks and loop devices, so drop the test with it.
Link: https://patch.msgid.link/20260917-work-put_mnt_ns-revert-v1-1-34d9b8679e68@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>