[BUG] Documentation prints warnings when building with `BKR_PY3=1 make`

[mdujava]

Describe the bug
Using release-28 or develop branch to build documentation will cause some working to be printed.

28.3

To Reproduce
Steps to reproduce the behavior:

1. Clone repo
2. checkout release-28 or develop branch
3. BKR_PY=1 make clean build
4. warnings shown:

WARNING: unknown directive or role name: http:patch
/root/beaker/documentation/whats-new/release-0.16.rst:45: ERROR: Unknown interpreted text role "http:patch".
WARNING: unknown directive or role name: http:get
/root/beaker/documentation/whats-new/release-0.17.rst:166: ERROR: Unknown interpreted text role "http:get".

Additional context
Extension sphinxcontrib.httpdomain is missing in documentation/conf.py as well as in beaker.spec as a BuildRequires: