Fix tests for Julia v1.4-rc1

[blegat]

Closes #1000

[blegat]

The tests are failing now due to the change in JuliaLang/julia#33205

[codecov-io]

Codecov Report

Merging #1010 into master will increase coverage by 0.01%.
The diff coverage is 75%.

@@            Coverage Diff            @@
##           master   #1010      +/-   ##
=========================================
+ Coverage   95.18%   95.2%   +0.01%     
=========================================
  Files          99      99              
  Lines       11240   11250      +10     
=========================================
+ Hits        10699   10710      +11     
+ Misses        541     540       -1

Impacted Files	Coverage Δ
src/Utilities/functions.jl	93.2% <75%> (+0.05%)	⬆️
src/FileFormats/MOF/MOF.jl	100% <0%> (ø)	⬆️
src/FileFormats/MPS/MPS.jl	99.23% <0%> (ø)	⬆️
src/FileFormats/LP/LP.jl	97.82% <0%> (+0.02%)	⬆️
src/FileFormats/utils.jl	95.52% <0%> (+0.06%)	⬆️
src/Utilities/mutable_arithmetics.jl	90% <0%> (+0.1%)	⬆️
src/Utilities/constraints.jl	100% <0%> (+14.28%)	⬆️

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