Removing or changing x-camara-commonalities extension field

[rartych]

Problem description
x-camara-commonalities field was introduced to info object in version 0.4, but it occurs that it is hard to maintain esp. when Commonalities produce patch release.

Expected behavior
Remove x-camara-commonalities field from info object definition in API Design Guidelines.
Release notes and Changelog include reference to the Commonalities release available when API is published.
Additionally, the same information can be mentioned in API Readiness Checklist point 2

Alternative solution
Indicate only Commonalities release major number (r1) or version without patch (0.5).

Additional context

The issue was raised during TSC meeting.