Replace non-hyphen minus sign (Julia compatibility)

[pmartorell]

Replacing the minus sign "−" (U+2212) to "-" (U+002D).

This PR improves backward compatibility of Julia. The sign "−" (U+2212) (\minus) is only available on Julia 1.7 or newer:

https://github.com/JuliaLang/julia/blob/v1.9.4/HISTORY.md#language-changes-1

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (10d0b59) 88.10% compared to head (5d718c4) 88.10%.

Files	Patch %	Lines
src/ODEs/ODETools/Tableaus.jl	0.00%	6 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #966   +/-   ##
=======================================
  Coverage   88.10%   88.10%           
=======================================
  Files         177      177           
  Lines       21077    21077           
=======================================
  Hits        18569    18569           
  Misses       2508     2508           

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[JordiManyer]

@pmartorell The ODEs module is being refactored soon... I would wait for PR #965 to be merged before doing this.

[AlexandreMagueresse]

Hi @pmartorell , I had seen these nonstandard minus signs too and I replaced them when rewriting the ODE module in PR #965, more precisely here.

[pmartorell]

Thanks @AlexandreMagueresse, I close this PR since it is already considered in #965