Changed rounding method

[Alexander-Sol]

As it turns out, there is a very good reason that Math.Round() uses MidpointRounding.RoundToEven as the default method of rounding. For more information, see here:n https://learn.microsoft.com/en-us/dotnet/api/system.math.round?view=net-9.0

This PR amends the mzML writer rounding PR (#821) to use the default rounding method.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.76%. Comparing base (de68239) to head (b9ae8f1).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #826   +/-   ##
=======================================
  Coverage   77.76%   77.76%           
=======================================
  Files         230      230           
  Lines       34166    34166           
  Branches     3540     3540           
=======================================
  Hits        26569    26569           
  Misses       6991     6991           
  Partials      606      606           

Files with missing lines	Coverage Δ
mzLib/MassSpectrometry/MzSpectra/MzSpectrum.cs	91.38% <100.00%> (ø)

[trishorts]

some itraq failures.

[nbollis]

some itraq failures.

Those are my bad. They are fixed by my PR