selftests: tc-testing: remove unnecessary time.sleep

This operation is redundant and it's not stabilizing nor waiting
for anything.

Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20231124154248.315470-3-pctammela@mojatatu.com


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