Alerting: Fix misleading status code in provisioning API

[usommerl]

Fixes #66249

Which issue(s) does this PR fix?: Fix misleading status code in provisioning API

[CLAassistant]

All committers have signed the CLA.

[grafanabot]

Hello @grobinson-grafana!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[grafanabot]

Hello @grobinson-grafana!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[grobinson-grafana]

Thank you very much for creating this! I will take a look tomorrow!

[grobinson-grafana]

LGTM! You can expect to see this fix in the next minor version of 9.4 and 9.5, and also 10.0.