[dv/dvsim] Fix when next_item does not have dependency
[dv/dvsim] Fix when next_item does not have dependency

This PR fixes the comment in PR #4993. Thanks @rupert for the
suggestion.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan