ipynb CI jobs timing out

[FedeMPouzols]

This seems to be happening again. It looks similar to the issue that was fixed in #501.

Examples from recent timeouts. The two first one happened for [NbConvertApp] Converting notebook ALMA_SD.ipynb to notebook, but the third one was for [NbConvertApp] Converting notebook VLBA.ipynb to notebook:

#530 => https://github.com/casangi/xradio/actions/runs/23983593481/job/69953467794?pr=530

nbclient.exceptions.CellTimeoutError: A cell timed out while it was being executed, after 1800 seconds.
The message was: Cell execution timed out.
Here is a preview of the cell contents:
-------------------
['from xradio.measurement_set import convert_msv2_to_processing_set', 'ms_file = "venus_ephem_test.ms"', '', 'main_chunksize = {"frequency": 1, "time": 20}  # baseline, polarization', 'outfile = "venus_ephem_test.ps.zarr"']
...
['    out_file=outfile,', '    parallel_mode="none",', "    persistence_mode='w',", '    main_chunksize=main_chunksize,', ')']
-------------------

#555 => https://github.com/casangi/xradio/actions/runs/23983593481/job/69953467794?pr=530

nbclient.exceptions.CellTimeoutError: A cell timed out while it was being executed, after 1800 seconds.
The message was: Cell execution timed out.
Here is a preview of the cell contents:
-------------------
from toolviper.dask import local_client

viper_client = local_client(cores=4, memory_limit="4GB")
viper_client

#553 => https://github.com/casangi/xradio/actions/runs/23795906841/job/69342990199

nbclient.exceptions.CellTimeoutError: A cell timed out while it was being executed, after 1800 seconds.
The message was: Cell execution timed out.
Here is a preview of the cell contents:
-------------------
['from xradio.measurement_set import convert_msv2_to_processing_set', '', 'ms_file = "VLBA_TL016B_split.ms"', '', 'main_chunksize = {"frequency": 1, "time": 20}  # baseline, polarization']
...
['    parallel_mode="none",', '    partition_scheme=["FIELD_ID"],', "    persistence_mode='w',", '    main_chunksize=main_chunksize,', ')']
-------------------