Fix chunked body decoding

[rkistner]

Description

Closes #2325.

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• All new and existing tests passed, including Rubocop. Only ran tests in test/test_puma_server.rb locally

[nateberkopec]

Thanks for your contribution!

[nateberkopec]

Merged: 3cdf905

[dentarg]

For completeness, the two other commits: a2f5199, 552e8b5