refactor: Use context manager to read gzip batch files

[edgarrmondragon]

---

📚 Documentation preview 📚: https://meltano-sdk--2628.org.readthedocs.build/en/2628/

[codspeed-hq]

CodSpeed Performance Report

Merging #2628 will not alter performance

_{Comparing edgarrmondragon/refactor/use-context-read-gzip (a2d6c55) with main (ddb922a)}

Summary

✅ 6 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 89.67%. Comparing base (ddb922a) to head (a2d6c55).

Files	Patch %	Lines
singer_sdk/sinks/core.py	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2628      +/-   ##
==========================================
- Coverage   89.71%   89.67%   -0.04%     
==========================================
  Files          58       58              
  Lines        4853     4854       +1     
  Branches      948      950       +2     
==========================================
- Hits         4354     4353       -1     
- Misses        349      350       +1     
- Partials      150      151       +1     

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