[Go SDK]: Retrieve element type from input PCollection in parquetio.Write

[johannaojeling]

Removes the t reflect.Type parameter from parquetio.Write and derives the element type from the input PCollection instead. Fixes #28490.

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[codecov]

Codecov Report

Merging #28491 (f9c5a71) into master (52abb14) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #28491      +/-   ##
==========================================
- Coverage   72.23%   72.23%   -0.01%     
==========================================
  Files         684      684              
  Lines      100855   100856       +1     
==========================================
- Hits        72854    72851       -3     
- Misses      26422    26428       +6     
+ Partials     1579     1577       -2     

Flag	Coverage Δ
go	53.42% <100.00%> (-0.01%)	⬇️

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Files Changed	Coverage Δ
sdks/go/pkg/beam/io/parquetio/parquetio.go	68.65% <100.00%> (+0.47%)	⬆️

... and 2 files with indirect coverage changes

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[lostluck]

Thanks!

I don't love backwards incompatible changes, but this is an improvement.