Bump OkHttp to 5.x

Upgrade the OkHttp version used for compilation from 4.9.2 to 5.x.

OkHttp 5.x is Kotlin-based and supports multiple `EventListener` instances. Prior upgrade attempts may have had failing tests.

Locate the dependency declaration that currently uses OkHttp 4.9.2 and inspect the existing tests around its usage. Run the relevant test suite before and after the upgrade, then confirm the project compiles with OkHttp 5.x and that the previously failing tests pass.

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