Fix UndefVar on dropout GPU test

Author: darsnack

test/cuda/layers.jl

@@ -282,7 +282,7 @@ end
 end
 
 @testset "Dropout RNGs" begin
-  @test_throws ArgumentError dropout(MersenneTwister(), CUDA.rand(Float32, 2, 3), 0.1)
+  @test_throws ArgumentError Flux.dropout(MersenneTwister(), CUDA.rand(Float32, 2, 3), 0.1)
   @testset for layer in (Dropout, AlphaDropout)
     m = layer(0.1; rng = MersenneTwister(123))
     @test_throws ErrorException gpu(m)

test/cuda/runtests.jl

@@ -1,6 +1,7 @@
 using Flux, Test, CUDA
 using Zygote
 using Zygote: pullback
+using Random
 
 @info "Testing GPU Support"
 CUDA.allowscalar(false)