[AGIPD][CORRECT] Remove the default specification for caldb_root

Description

This MR removes the default value for caldb_root to return to the old behaviour for have None caldb_root and using the correct caldb path, e.g. for ONC.

This small MR addresses the issue in this ticket. The same issue was faced last week with AGIPD500K runner. Most probably this wont be used anyway and when we update the runners' deployment, we might already have the new CalibrationData API used. But in case we don't we might as well have a fixed bug.

How Has This Been Tested?

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

Reviewers

@tmichela @schmidtp