breakage from upstream averaging changes in africanus

[bennahugo]

for the moment this should probably be pinned to africanus codex-africanus==0.2.10 due to api changes - reported by @SharmilaGoedhart

ragavi-vis --ms 1663866015_sdp_l0.ms  --xaxis time --yaxis  amp 
05.10.2022@12:24:05 - ragavi               - ERROR      - Oops ... uncaught exception occurred!
05.10.2022@12:24:05 - ragavi               - ERROR      - Traceback (most recent call last):
05.10.2022@12:24:05 - ragavi               - ERROR      -    File "/scratch2/sharmila/venv-shadems/bin/ragavi-vis", line 20, in <module>
05.10.2022@12:24:05 - ragavi               - ERROR      -     from ragavi.visibilities import main
05.10.2022@12:24:05 - ragavi               - ERROR      -    File "/scratch2/sharmila/venv-shadems/lib/python3.8/site-packages/ragavi/visibilities.py", line 34, in <module>
05.10.2022@12:24:05 - ragavi               - ERROR      -     from ragavi.averaging import get_averaged_ms
05.10.2022@12:24:05 - ragavi               - ERROR      -    File "/scratch2/sharmila/venv-shadems/lib/python3.8/site-packages/ragavi/averaging.py", line 21, in <module>
05.10.2022@12:24:05 - ragavi               - ERROR      -     from africanus.averaging.dask import (time_and_channel,
05.10.2022@12:24:05 - ragavi               - ERROR      -  ImportError: cannot import name 'chan_metadata' from 'africanus.averaging.dask' (/scratch2/sharmila/venv-shadems/lib/python3.8/site-packages/africanus/averaging/dask.py)