Don't adapt opaque closures

[codecov[bot]]

Codecov Report

Patch coverage: 75.00% and project coverage change: +0.47 :tada:

Comparison is base (47f5040) 82.85% compared to head (cc2829f) 83.33%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #63 +/- ## ========================================== + Coverage 82.85% 83.33% +0.47% ========================================== Files 6 6 Lines 70 72 +2 ========================================== + Hits 58 60 +2 Misses 12 12 ``` | [Impacted Files](https://app.codecov.io/gh/JuliaGPU/Adapt.jl/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaGPU) | Coverage Δ | | |---|---|---| | [src/base.jl](https://app.codecov.io/gh/JuliaGPU/Adapt.jl/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaGPU#diff-c3JjL2Jhc2Uuamw=) | `87.50% <0.00%> (-5.84%)` | :arrow_down: | | [ext/AdaptStaticArraysExt.jl](https://app.codecov.io/gh/JuliaGPU/Adapt.jl/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaGPU#diff-ZXh0L0FkYXB0U3RhdGljQXJyYXlzRXh0Lmps) | `100.00% <100.00%> (+100.00%)` | :arrow_up: | | [src/Adapt.jl](https://app.codecov.io/gh/JuliaGPU/Adapt.jl/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaGPU#diff-c3JjL0FkYXB0Lmps) | `100.00% <100.00%> (ø)` | |

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