[GH-92] Fixed temp file and batch size for fetch_uniprot_metadata.py

[GallVp]

PR checklist

• Fixes fetch_uniprot_metadata.py returns bad request from an empty temp file #92
• When the temp file was empty, pandas read_csv failed. 300 for the UniProt API batch size was not working anymore. I reduced it to 100.
• I tested the code with the example input file provided in fetch_uniprot_metadata.py returns bad request from an empty temp file #92
• If you've added new software dependencies, make sure that those dependencies are included in the appropriate conda environments.
• If you've added new functionality, make sure that the documentation is updated accordingly.
• If you encountered bugs or features that you won't address, but should be addressed eventually, create new issues for them.

[keithchev]

@GallVp Thanks so much for fixing this!

[keithchev]

I think we can merge this as-is. The CI is failing but only because of a deprecated workflow version, which we'll need to fix that in a subsequent PR. I tested this PR manually and also ran the tests locally.

For extra clarity for the record, this PR fixes two essentially unrelated problems in fetch_uniprot_metadata.py:

• It decreases the batch size used to query the UniProt API from 300 to 100. Since we know the old batch size of 300 used to work, this presumably reflects a change made on the UniProt side.
• It fixes a bug that caused the script to crash when the temp file used to cache previously fetched accessions was empty (which only happened if the script failed to retrieve any accessions and then also crashed, leaving an empty temp file behind).