Update test/core/adjoint_tests.jl

Co-authored-by: Christopher Rackauckas <accounts@chrisrackauckas.com>

Author: m-bossart

test/core/adjoint_tests.jl

@@ -13,7 +13,7 @@
     p = [3.0, 2.0]
 
     ∂p_zygote = only(Zygote.gradient(solve_nlprob, p))
-    #∂p_forwarddiff = ForwardDiff.gradient(solve_nlprob, p)
+    ∂p_forwarddiff = ForwardDiff.gradient(solve_nlprob, p)
     ∂p_tracker = Tracker.data(only(Tracker.gradient(solve_nlprob, p)))
     ∂p_reversediff = ReverseDiff.gradient(solve_nlprob, p)
     @test ∂p_zygote ≈ ∂p_tracker ≈ ∂p_reversediff