Fix show for Fun in an ArraySpace

[jishnub]

This removes the show method for Fun{<:Union{ConstantSpace, ArraySpace{<:ConstantSpace}}}, as the special cases were becoming unwieldy to maintain

Fixes the display for

julia> D2 = Dirichlet(Chebyshev(),1);

julia> D2 * Fun()
Fun(ApproxFunBase.ArraySpace(ConstantSpace{Point{Float64}, Float64}[ConstantSpace(Point(-1.0)), ConstantSpace(Point(1.0))]), [1.0])

[codecov[bot]]

Codecov Report

Patch coverage: 57.14% and project coverage change: -0.10% :warning:

Comparison is base (614f040) 27.62% compared to head (ff2e6d6) 27.53%. Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #556 +/- ## ========================================== - Coverage 27.62% 27.53% -0.10% ========================================== Files 80 80 Lines 8387 8379 -8 ========================================== - Hits 2317 2307 -10 - Misses 6070 6072 +2 ``` | [Files Changed](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/556?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/Operators/SubOperator.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/556?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9TdWJPcGVyYXRvci5qbA==) | `42.64% <25.00%> (ø)` | | | [src/Operators/functionals/Evaluation.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/556?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9mdW5jdGlvbmFscy9FdmFsdWF0aW9uLmps) | `43.47% <100.00%> (ø)` | | | [src/show.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/556?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL3Nob3cuamw=) | `62.96% <100.00%> (-3.42%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/556/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation)

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