BugFix: file_format in ReactionDrawer

[alongd]

These are leftovers from the PEP8 conversions where the reserved keyword format was replaced with file_format in draw.py.
This fixed was verified to function correctly (within ARC).

[codecov]

Codecov Report

Merging #1760 into master will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           master   #1760   +/-   ##
======================================
  Coverage    32.6%   32.6%           
======================================
  Files          87      87           
  Lines       26115   26115           
  Branches     6875    6875           
======================================
  Hits         8516    8516           
+ Misses      16641   16629   -12     
- Partials      958     970   +12

Impacted Files	Coverage Δ
rmgpy/molecule/draw.py	40.17% <0%> (ø)	⬆️
rmgpy/data/statmech.py	42.2% <0%> (ø)	⬆️
rmgpy/rmg/pdep.py	12.21% <0%> (ø)	⬆️
rmgpy/reaction.py	0% <0%> (ø)	⬆️
rmgpy/data/kinetics/family.py	48.28% <0%> (ø)	⬆️
rmgpy/yml.py	15.71% <0%> (ø)	⬆️
rmgpy/data/kinetics/database.py	50.61% <0%> (ø)	⬆️
rmgpy/molecule/molecule.py	0% <0%> (ø)	⬆️
rmgpy/statmech/ndTorsions.py	59.78% <0%> (ø)	⬆️

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[mliu49]

This fix is already part of #1735.

[alongd]

Great! I'll go ahead and close this PR.