Change dihedral phi to integer in lammpsdata.py as required by LAMMPS.

[rwsmith7531]

PR Summary:

The phi dihedral parameter is written as a float in lammpsdata.py, which would make sense due to it representing an angle in degrees, but LAMMPS requires that it be written as an integer, so this PR updates _write_dihedral_information such that the phi parameter is written as an integer.

Closes #1091

PR Checklist

---

• Includes appropriate unit test(s)
• Appropriate docstring(s) are added/updated
• Code is (approximately) PEP8 compliant
• Issue(s) raised/addressed?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.97%. Comparing base (ab6d54d) to head (28056bb).
Report is 61 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1092      +/-   ##
==========================================
- Coverage   89.39%   84.97%   -4.43%     
==========================================
  Files          61       61              
  Lines        6235     6235              
==========================================
- Hits         5574     5298     -276     
- Misses        661      937     +276     

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[thangckt]

This problem has been solved in #1098