update fastpow test

Author: ChrisRackauckas

test/fastpow.jl

@@ -1,4 +1,4 @@
-using DiffEqBase: fastlog2, _exp2, fastpow
+using DiffEqBase: fastlog2, fastpow
 using Enzyme, EnzymeTestUtils
 using Test
 
@@ -8,12 +8,6 @@ using Test
     end
 end
 
-@testset "Exp2" begin
-    for x in -100:0.01:3
-        @test exp2(x)≈_exp2(Float32(x)) atol=1e-6
-    end
-end
-
 @testset "Fast pow" begin
     @test fastpow(1, 1) isa Float32
     @test fastpow(1.0, 1.0) isa Float32