Update to cal_db_interactive version 1.6.4

One of the smallest MRs ever. As discussed on issue 221 on the calibration workshop, cal_db_interactive should set actual package version. This is now done (https://git.xfel.eu/gitlab/detectors/cal_db_interactive/merge_requests/57) and so the tag 1.6.4 should match package version 1.6.4. This should, in turn, make upgrading pycalibration smoother.

How it's been tested

In a venv where the current master of pycalibration was prerviously installed:

(venv) hammerd@max-exfl-display001.desy.de:~/221/pycalibration
> pip install -r requirements.txt                                                                                                                 
[lots of boring output]
Installing collected packages: iCalibrationDB
  Found existing installation: iCalibrationDB 0.1
    Uninstalling iCalibrationDB-0.1:
      Successfully uninstalled iCalibrationDB-0.1
  Running setup.py install for iCalibrationDB ... done
Successfully installed iCalibrationDB-1.6.4

And indeed:

(venv) hammerd@max-exfl-display001.desy.de:~/221/pycalibration
> python                                                                                                                                          0 [11:41:34]
Python 3.6.8 (default, Apr  2 2020, 13:34:55) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
Type "help", "copyright", "credits" or "license" for more information.
> import iCalibrationDB
> iCalibrationDB.__version__
'1.6.4'

Reviewers

@ahmedk @danilevc sorry for distracting you with a one-line diff, I just figured I'd finally close https://git.xfel.eu/gitlab/detectors/calibration_workshop/issues/221.