Although we have deferred the Arb upgrade to Sage 9.3, on various platforms (e.g. ubuntu-groovy-standard, https://github.com/sagemath/sage/runs/1058929422) we are already getting the doctest failures because system Arb is 2.18.

Hence we need to adjust the doctests (see #28623) already in Sage 9.2 - so that they work with both the older and the newer version.

CC: @fredrik-johansson @mezzarobba @videlec @kiwifb @antonio-rojas @dimpase

Component: doctest coverage

Author: Dima Pasechnik

Branch/Commit: 464f08a

Reviewer: François Bissey

Issue created by migration from https://trac.sagemath.org/ticket/30486