Remove OWNERS files

[damccorm]

Per https://lists.apache.org/thread/8smb6hv8s9ldvsfxcbhzx7wd2mpl7op1 we don't need OWNERS files anymore. Instead we can use the reviewer bot config to manage code ownership/affinity (https://github.com/apache/beam/blob/master/.github/REVIEWERS.yml)

Changes here shouldn't be merged until we get consensus in that thread.

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[codecov]

Codecov Report

Merging #27896 (b8f2254) into master (0f847ef) will decrease coverage by 0.29%.
Report is 10 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #27896      +/-   ##
==========================================
- Coverage   70.87%   70.59%   -0.29%     
==========================================
  Files         861      857       -4     
  Lines      105010   103938    -1072     
==========================================
- Hits        74422    73370    -1052     
+ Misses      29030    29010      -20     
  Partials     1558     1558              

Flag	Coverage Δ
go	53.70% <ø> (-0.01%)	⬇️
python	79.55% <ø> (-0.29%)	⬇️

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see 27 files with indirect coverage changes

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[github-actions]

Assigning reviewers. If you would like to opt out of this review, comment assign to next reviewer:

R: @AnandInguva for label python.
R: @Abacn for label java.
R: @jrmccluskey for label go.
R: @Abacn for label build.
R: @pabloem for label io.

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