Update iir_filter.ipynb and rerun other ipynb.

applications/lofar2/model/pfb_os/filter_design_firls.ipynb

applications/lofar2/model/pfb_os/filter_design_remez.ipynb

...ons/lofar2/model/pfb_os/filter_design_windowed_sync.ipynb

...s/lofar2/model/pfb_os/hilbert_transform_application.ipynb

...ations/lofar2/model/pfb_os/hilbert_transform_design.ipynb

applications/lofar2/model/pfb_os/iir_filter.ipynb

...ofar2/model/pfb_os/rectangular_window_and_ideal_lpf.ipynb