fix printing of arrays of affine expressions

[lucaferranti]

PR description

Before, printing arrays of affine xpressions was using too many decimals, making it hard to read.

Before

julia> @affinevars x y;

julia> [x+1/6*y-1 1/3*x+1/7;-x-1/9 1/11]
2×2 Matrix{AffineExpression{Float64}}:
 x+0.16666666666666666y-1.0  0.3333333333333333x+0.14285714285714285
 -x-0.1111111111111111       0.09090909090909091

After

julia> @affinevars x y;

julia> [x+1/6*y-1 1/3*x+1/7;-x-1/9 1/11]
2×2 Matrix{AffineExpression{Float64}}:
 x+0.166667y-1.0  0.333333x+0.142857
 -x-0.111111      0.0909091

Related issues

Checklist

• [x] Updated/added tests
• [ ] Updated/added docstring (needed only for exported functions)
• [x] Updated Project.toml

Other

[codecov-commenter]

Codecov Report

Merging #123 (cfcc162) into main (80c6d65) will increase coverage by 0.01%. The diff coverage is 95.23%.

@@            Coverage Diff             @@
##             main     #123      +/-   ##
==========================================
+ Coverage   97.02%   97.04%   +0.01%     
==========================================
  Files          17       17              
  Lines         639      643       +4     
==========================================
+ Hits          620      624       +4     
  Misses         19       19              

Impacted Files	Coverage Δ
src/pils/affine_expressions.jl	98.79% <95.23%> (+0.06%)	:arrow_up:

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