Restrict SciMLBase compat to <2.68.0

SciMLBase.remake is called twice during the cache initialization
for a problem with the multirate alg.

SciMLBase changed the way remake(::AbstractODEProblem,...)
works in 2.68.0. Previously, if the f kwarg was an AbstractODEFunction,
the problem was remade with f directly as its function.
After 2.68.0, remake(::AbstractODEProblem) calls a new remake method with
f and prob.f as arguments. This new function returns an
AbstarctSciMLFunction of the same type and properties as prob.f.

Project.toml

@@ -47,7 +47,7 @@ OrderedCollections = "1"
 PrettyTables = "2"
 Random = "1"
 SafeTestsets = "0.1"
-SciMLBase = "1, 2"
+SciMLBase = "< 2.68.0"
 StaticArrays = "1"
 StatsBase = "0.33, 0.34"
 Test = "1"