[v253] Drop log level of header limits log message

[yuwata]

Especially when using in-memory logging, these are too noisy so let's drop them back to debug level.

(cherry picked from commit afc47ee)

[packit-as-a-service]

We were not able to find or create Copr project packit/systemd-systemd-stable-469 specified in the config with the following error:

Cannot create a new Copr project (owner=packit project=systemd-systemd-stable-469 chroots=[]): chroots: '[]' is not a valid choice for this field..

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Unless the HTTP status code above is >= 500, please check your configuration for:

1. typos in owner and project name (groups need to be prefixed with @)
2. whether the project name doesn't contain not allowed characters (only letters, digits, underscores, dashes and dots must be used)
3. whether the project itself exists (Packit creates projects only in its own namespace)
4. whether Packit is allowed to build in your Copr project
5. whether your Copr project/group is not private