shorten timespan on initdt test

This previously was testing that you don't get a warning even though the solution was `Inf`. The only reason it worked at all is that `Euler` is simple enough that it stayed `Inf` rather than going to `NaN` and DiffEqBase incorrectly didn't consider `Inf` to be diverged.

Author: Oscar Smith

test/interface/ode_initdt_tests.jl

@@ -21,7 +21,7 @@ dt₀ = sol3.t[2]
 T = Float32
 u0 = T.([1.0; 0.0; 0.0])
 
-tspan = T.((0, 100))
+tspan = T.((0, 70))
 prob = remake(prob, u0 = u0, tspan = tspan)
 @test_nowarn solve(prob, Euler(); dt = T(0.0001))