Another fix in the usage of MixedIntegerLinearProgram in sage.graphs.graph_coloring #32536
Description
Part of #32191 (Meta-ticket: Audit/fix all uses of MixedIntegerLinearProgram in sage.combinat, sage.graphs).
Here we avoid the use of Integer(round(p.solve(...))) whenever possible.
CC: @slel
Component: graph theory
Author: David Coudert
Branch/Commit: 2438851
Reviewer: Matthias Koeppe
Issue created by migration from https://trac.sagemath.org/ticket/32536