Remove Tensorflow from default Beam images.

[tvalentyn]

Including TF significantly increases the size of default Beam container images. Given that some Beam users use other ML framework, including TF but not other, equally large dependencies, seems less obvious.

I suggest we remove TF for now, which shaves almost 1.5 GB from unpacked image.

If you have been negatively affected by this change, please comment on #20605 - we would like to collect user input to prioritize this effort accordingly.

For tips on Python runtime dependency management, see : https://beam.apache.org/documentation/sdks/python-pipeline-dependencies.

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[lostluck]

The 2.50 images were around 4.13GB (according to my local docker). What's the new total without tensor flow? (It would be good to have in the PR description anyway).

[codecov]

Codecov Report

Merging #28424 (f679ff8) into master (846a1ab) will increase coverage by 0.01%.
Report is 6 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #28424      +/-   ##
==========================================
+ Coverage   72.33%   72.35%   +0.01%     
==========================================
  Files         682      682              
  Lines      100541   100541              
==========================================
+ Hits        72730    72748      +18     
+ Misses      26238    26216      -22     
- Partials     1573     1577       +4     

Flag	Coverage Δ
go	53.66% <ø> (+0.04%)	⬆️
python	82.87% <ø> (+<0.01%)	⬆️

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[tvalentyn]

The 2.50 images were around 4.13GB (according to my local docker). What's the new total without tensor flow? (It would be good to have in the PR description anyway).

This number (unpacked image) reduces to 2.67 GB

[bvolpato]

It makes sense to me. LGTM.

Might be good to send a note to users@ and/or highlight this when the release is coming out

[github-actions]

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