Fix reading manifest file when it's only one line and also served by GitHub

[ivirshup]

For some reason changing the size of our manifest file has broken our code to read it. It has something to do with how the file is encoded. I believe it is related to fsspec/filesystem_spec#389.

The issue only comes up due to some handling of partial reads. So I switched to doing a full read since the file is never that large.

We use fsspec instead of requests since sometimes we read a local file or one from s3.

[ivirshup]

Cleaner version:

blocklist = (
    # Figure out protocol to open file
    fsspec.filesystem(
        fsspec.utils.infer_storage_options(dataset_id_blocklist_uri)["protocol"]
    )
    # Read whole file as bytes
    .cat_file(dataset_id_blocklist_uri)
    # Decode to string and split into lines
    .decode("utf-8").strip().split("\n")
)

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.36%. Comparing base (f32c274) to head (908423c).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ls/cellxgene_census_builder/tests/test_manifest.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1323   +/-   ##
=======================================
  Coverage   91.36%   91.36%           
=======================================
  Files          82       82           
  Lines        6482     6482           
=======================================
  Hits         5922     5922           
  Misses        560      560           

Flag	Coverage Δ
unittests	91.36% <92.30%> (ø)

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[ivirshup]

I did not touch the code that mypy is complaining about so I am okay with skipping it for this PR