Fix deprecation warning with viewing KR crystals

[tscrim]

We have the following:

sage: K = crystals.KirillovReshetikhin(['A',2,1], 2,1)
sage: view(K)
/sage-build/local/lib/python3.9/site-packages/sage/misc/decorators.py:491:
 DeprecationWarning: parameter {'backward':True} (in edge_options) is deprecated.
 Use {'dir':'back'} instead.
See https://trac.sagemath.org/31381 for details.
  return func(*args, **options)

We update the edge option function according to #31381.

CC: @sagetrac-sage-combinat @dwbump @anneschilling @nthiery @fchapoton @seblabbe

Component: combinatorics

Keywords: crystals, latex

Author: Travis Scrimshaw

Branch/Commit: 0354a41

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/31719

[tscrim]

comment:1

Simple fix.

---

New commits:

0354a41

Fix deprecation warning for viewing crystals with graphviz.

[tscrim]

Branch: public/crystals/fix_edge_options-31719

[tscrim]

Commit: 0354a41

[fchapoton]

comment:2

ok

[fchapoton]

Reviewer: Frédéric Chapoton

[tscrim]

comment:3

Thank you.

[vbraun]

Changed branch from public/crystals/fix_edge_options-31719 to 0354a41