Remove wrong import in FF AGIPD notebook

A fix for a reported bug at https://in.xfel.eu/redmine/issues/124675#change-463210

As the agipdlib.get_bias_voltage function was removed the code complains when trying to import it.

Description

How Has This Been Tested?

• being tested with the xfel-calibrate CL added by Marcin in the mentioned ticket

Relevant Documents (optional)

Types of changes

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

Checklist:

Reviewers

@schmidtp @roscar @danilevc

notebooks/AGIPD/Characterize_AGIPD_Gain_FlatFields_NBC.ipynb

 import numpy as np
 import sharedmem
 import XFELDetAna.xfelpyanatools as xana
-from cal_tools.agipdlib import get_bias_voltage
 from cal_tools.agipdutils_ff import (
     BadPixelsFF,
     any_in,
 module = modules[0]
 %% Cell type:code id: tags:
 ``` python
-# This is never used in this notebook and should be removed
-
-# if bias_voltage == 0:
-#     # Read the bias voltage from files, if recorded.
-#     # If not available, make use of the historical voltage the detector is running at
-#     control_filename = f'{raw_folder}/r{run:04d}/RAW-R{run:04d}-{karabo_da_control}-S00000.h5'
-#     bias_voltage = get_bias_voltage(control_filename, karabo_id_control)
-#     bias_voltage = bias_voltage if bias_voltage is not None else 300
-# print(f"Bias voltage: {bias_voltage}V")
-%% Cell type:code id: tags: