Fix show for QuotientSpace

[jishnub]

Fix for bug introduced by #781. After this, the following work:

julia> QuotientSpace(Dirichlet(Chebyshev()))
Chebyshev() /
 1.0  -1.0  1.0  -1.0  1.0  -1.0  1.0  -1.0  1.0  -1.0  ⋯
 1.0   1.0  1.0   1.0  1.0   1.0  1.0   1.0  1.0   1.0  ⋯

julia> show(Q)
Chebyshev() /
ConcreteDirichlet : Chebyshev() → 2-element ArraySpace:
ConstantSpace{DomainSets.Point{Float64}, Float64}[ConstantSpace(Point(-1.0)), ConstantSpace(Point(1.0))]

[codecov]

Codecov Report

Merging #785 (d55e833) into master (7968dab) will increase coverage by 3.55%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #785      +/-   ##
==========================================
+ Coverage   31.29%   34.85%   +3.55%     
==========================================
  Files          15       15              
  Lines         850      855       +5     
==========================================
+ Hits          266      298      +32     
+ Misses        584      557      -27     

Impacted Files	Coverage Δ
src/Extras/show.jl	38.55% <100.00%> (+18.67%)	⬆️

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