Fix failing docstring in random testing for quaternion_algebra.py

[GiacomoPope]

The current code:

sage: set_random_seed(558346185206384723433409773377632267)
sage: q = randrange(1,1000)
....: p = randrange(1,1000)
....: Quat.<i,j,k> = QuaternionAlgebra(-q, -p)
....: O0 = Quat.maximal_order()
....: while True:
....:     b = Quat.random_element()
....:     if gcd(b.reduced_norm(), Quat.discriminant()) == 1:
....:         break
....: O1 = (b * O0).left_order()
....: iso = O0.isomorphism_to(O1); iso
Ring endomorphism of Order of Quaternion Algebra (-667, -662) with base ring Rational Field with basis (1, 1/2 + 1/2*i, j, 1/2 + 11/58*i + 1/2*j + 1/58*k)
  Defn: i |--> i
        j |--> j
        k |--> k
sage: O0
Order of Quaternion Algebra (-667, -662) with base ring Rational Field with basis (1, 1/2 + 1/2*i, j, 1/2 + 11/58*i + 1/2*j + 1/58*k)
sage: O1
Order of Quaternion Algebra (-667, -662) with base ring Rational Field with basis (1, 1/2 + 1/2*i, j, 1/2 + 11/58*i + 1/2*j + 1/58*k)

Causes a doctest to fail as a Ring morphism is expected but when O0 == O1 then instead a Ring endomorphism is computed instead.

We simply truncate the expected output for the random testing from Ring morphism to Ring ... fixing the failure.

sage -t --random-seed=558346185206384723433409773377632267 src/sage/algebras/quatalg/quaternion_algebra.py
    [562 tests, 17.35 s]
----------------------------------------------------------------------
All tests passed!
----------------------------------------------------------------------
Total time for all tests: 18.7 seconds
    cpu time: 15.6 seconds
    cumulative wall time: 17.3 seconds

Fixes #37488

[GiacomoPope]

I don't know whether to label this as minor, as it's a small bug, or blocker, as it currently results in CI failure.

[yyyyx4]

Thanks, looks good enough to me. I guess blocker makes sense since it's a really trivial change (not much can go wrong by merging it), and the failure being present in a release could waste quite a few people's time.

[GiacomoPope]

Thanks Lorenz :)

[yyyyx4]

Relabelling to minor per this sage-devel thread, but it would still be nice to get this into the release @vbraun.

[GiacomoPope]

@vbraun following Lorenz's message -- this bug is causing repeated CI failures in my PR considering the tiny footprint of this PR it would be nice to get it included?

[github-actions]

Documentation preview for this PR (built with commit 949d94e; changes) is ready! 🎉