Bring algebras/free_algebra_quotient.py to 100% coverage

[sagetrac-jlopez]

Improve the doctest for algebras/free_algebra_quotient.py.

Component: doctest coverage

Reviewer: Javier López Peña

Issue created by migration from https://trac.sagemath.org/ticket/12593

[jhpalmieri]

comment:2

This file has 100% coverage already, so this ticket can be closed (as "works for me").

[jhpalmieri]

Reviewer: Javier López Peña