Fix transitive DoS vulnerability

[draial]

This PR aims to fix a transitive DoS vulnerability detected via the dependency okhttp:4.10.0 > okio:3.0.0. Version 3.4.0 contained a fix.

Sources:

• https://security.snyk.io/package/maven/com.squareup.okio:okio/3.0.0
• https://github.com/square/okhttp/blob/parent-4.10.0/build.gradle (okio:3.0.0)
• https://github.com/square/okhttp/blob/parent-4.11.0/build.gradle (okio:3.2.0)
• https://github.com/square/okhttp/blob/parent-4.12.0/build.gradle (okio:3.6.0)

The closest non-transitively-vulnerable okhttp version is 4.12.

[draial]

this is related to #205, but also updates the corresponding test library version

[beavuck]

@sdiakovskyi-gd @szagr

Pinging the latest two contributors I could find :) do you think this could make it into a version 5.2.6?

[mdmytrash]

Hello, @draial
Thank you for your contribution