Fix comment card removal

[paulromano]

The regex to find and remove comment cards currently breaks the following:

m1   1001.70c 1.0 &
code=0
m2   1001.70c 1.0

Namely, the regex doesn't enforce that the c character be following by one or more blanks (which is specified in the MCNP manual). This PR updates the regex to enforce that either the c is following by a space/tab, or that it is followed immediately by a newline character.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.23%. Comparing base (aa881ed) to head (fc227f4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #62   +/-   ##
=======================================
  Coverage   87.23%   87.23%           
=======================================
  Files           3        3           
  Lines         752      752           
  Branches      198      198           
=======================================
  Hits          656      656           
  Misses         52       52           
  Partials       44       44           

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