[cherry-pick][release-2.40.0] Rollback Dill from 3.5.1 to 3.1.1

[pabloem]

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[pabloem]

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[pabloem]

r: @ryanthompson591

[codecov]

Codecov Report

Merging #21911 (37bff61) into release-2.40.0 (3dc8c63) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@                Coverage Diff                 @@
##           release-2.40.0   #21911      +/-   ##
==================================================
- Coverage           74.01%   73.96%   -0.05%     
==================================================
  Files                 699      702       +3     
  Lines               92675    92858     +183     
==================================================
+ Hits                68592    68684      +92     
- Misses              22828    22919      +91     
  Partials             1255     1255              

Flag	Coverage Δ
python	83.56% <100.00%> (-0.10%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...hon/apache_beam/runners/dataflow/internal/names.py	100.00% <100.00%> (ø)
sdks/python/apache_beam/io/localfilesystem.py	90.97% <0.00%> (-0.76%)	⬇️
sdks/python/apache_beam/io/fileio.py	96.23% <0.00%> (-0.10%)	⬇️
sdks/python/apache_beam/ml/inference/base.py	95.29% <0.00%> (ø)
sdks/python/apache_beam/ml/inference/__init__.py	100.00% <0.00%> (ø)
...thon/apache_beam/ml/inference/pytorch_inference.py	0.00% <0.00%> (ø)
...thon/apache_beam/ml/inference/sklearn_inference.py	95.23% <0.00%> (ø)
..._beam/testing/benchmarks/nexmark/queries/query3.py	0.00% <0.00%> (ø)
...examples/inference/pytorch_image_classification.py	0.00% <0.00%> (ø)
...examples/inference/sklearn_mnist_classification.py	47.50% <0.00%> (ø)
... and 16 more

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