Removing support for okhttp2

[luc-leclerc]

Description

Removing module logbook-okhttp2

Motivation and Context

• okhttp 2.7.5 was deprecated long time ago, and remains a liability that may break and would takes time and effort to fix, rather than focusing on adding new features.
• The alternative exist, to use older logbook version or to use the more recent module logbook-okhttp (which use 4.12.0)

Relevant reference

• https://square.github.io/okhttp/changelogs/changelog_3x/#version-300-rc1
• https://github.com/square/okhttp

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [X] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [X] My change requires a change to the documentation.
• [X] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.