Bug#1121012: transition: numerical stack scotch to petsc

[Drew Parsons <dparsons@debian.org>]

Package: release.debian.org
Followup-For: Bug #1121012

With scotch 7.0.10-6 fixing metis compatibility links,
and Paul's manual activation testing binNMU libraries,
all packages for this transition are now migrated to testing.

So we can consider this transition complete.

Towards the weekend I'd like to continue on with the fenicsx 0.10 transition
(fenics-dolfinx and company), if there's no objections.
Collectively the fenics suite is a leaf node, so we don't need to
consider it a formal transition as such.

Drew