Add kernel to EnsembleGPUKernel documentaion

Author: murenkov

src/algorithms.jl

@@ -146,7 +146,7 @@ prob = ODEProblem{false}(lorenz, u0, tspan, p)
 prob_func = (prob, i, repeat) -> remake(prob, p = (@SVector rand(Float32, 3)) .* p)
 monteprob = EnsembleProblem(prob, prob_func = prob_func, safetycopy = false)
 
-@time sol = solve(monteprob, GPUTsit5(), EnsembleGPUKernel(), trajectories = 10_000,
+@time sol = solve(monteprob, GPUTsit5(), EnsembleGPUKernel(CUDA.CUDABackend()), trajectories = 10_000,
     adaptive = false, dt = 0.1f0)
 ```
 """