Bug Report: Upgrade Downgrade Testing - Backups - Manual is failing on release-16.0

[GuptaManan100]

Overview of the Issue

It was noticed that the test Upgrade Downgrade Testing - Backups - Manual is failing consistently for release-16.0 in the recent PRs.

An example failure run - https://github.com/vitessio/vitess/actions/runs/5403612380/jobs/9817949439#step:22:3691

On investigation it was found, that this test started failing because #12791 PR added the configuration --throttler-config-via-topo to the vttabet-up.sh script. However, on v15 vttablets this flag doesn't exist and causes an error like - unknown flag: --throttler-config-via-topo

Reproduction Steps

Run Upgrade Downgrade Testing - Backups - Manual in release-16.0

Binary Version

release-16.0

Operating System and Environment details

-

Log Fragments

No response