Changes

fix(prow-jobs/pingcap-qe/ci): fix git remote setup in periodic jobs (#3451)

This pull request includes changes to the
`prow-jobs/pingcap-qe/ci/periodics.yaml` file to modify the git remote
configuration commands.

Changes in git remote configuration:

* Updated the command to add a new git remote instead of setting the URL
for an existing remote. This change ensures that the remote is added
correctly if it doesn't already exist.
[[1]](diffhunk://#diff-627e88a7426360b8626ef9a0002f3558221924cb7e816f08afa52255839473d7L110-R110)
[[2]](diffhunk://#diff-627e88a7426360b8626ef9a0002f3558221924cb7e816f08afa52255839473d7L211-R211)
 (commit: 9e71c1d)