Nx - Random Normal - issue with defn

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# Random Normal - issue with defn

## Section

```elixir
Mix.install([
  {:exla, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "exla"},
  {:nx, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "nx", override: true}
])

Nx.Defn.global_default_options(compiler: EXLA)

defmodule RandomNormalTest do
  import Nx.Defn

  defn create_with_defn(shape) do
    Nx.random_normal(shape, 0.0, 1.0)
  end

  def create(shape) do
    Nx.random_normal(shape, 0.0, 1.0)
  end
end
```

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```
{:module, RandomNormalTest, <<70, 79, 82, 49, 0, 0, 9, ...>>, {:create, 1}}
```

```elixir
RandomNormalTest.create({10, 4})
```

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```
#Nx.Tensor<
  f32[10][4]
  [
    [0.36994102597236633, 0.07317788153886795, 0.49161645770072937, 2.0069003105163574],
    [-2.2546796798706055, -1.9848204851150513, -0.7559281587600708, -0.0988297164440155],
    [-0.2042686492204666, -0.4669297933578491, -0.4406200051307678, 0.25528794527053833],
    [-1.9771993160247803, -0.07872360944747925, 0.18106433749198914, -0.016550522297620773],
    [0.8465139865875244, -0.9714727401733398, -0.23460082709789276, -1.1613898277282715],
    [-1.0772348642349243, -0.058248281478881836, -1.6772676706314087, 0.6900256872177124],
    [-1.0431689023971558, -0.7773556113243103, -0.7354031205177307, 0.24952226877212524],
    [-0.04504086822271347, 0.3102203905582428, 0.8773104548454285, -0.26838353276252747],
    [1.846353530883789, -1.1995649337768555, 1.1605740785598755, -0.8619170784950256],
    [0.9801735281944275, -0.8678684234619141, -0.7064700126647949, -1.3400367498397827]
  ]
>
```

```elixir
# It works when the shape is given via a tensor
RandomNormalTest.create_with_defn(Nx.tensor([[0, 1], [2, 4]]))
```

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```
#Nx.Tensor<
  f32[2][2]
  [
    [0.49698734283447266, -0.4807703495025635],
    [0.6912095546722412, 0.10434946417808533]
  ]
>
```

```elixir
# It throws an error when the shape is set via a tuple
RandomNormalTest.create_with_defn({10, 4})
```