Fix RFO hessian update bug

[shoubhikraj]

Resolves #253

Hessian is updated in RFO, as Hessian is used for step instead of augmented Hessian

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Checklist

• The changes include an associated explanation of how/why
• Test pass
• Documentation has been updated
• Changelog has been updated

[codecov]

Codecov Report

Merging #254 (1238cdb) into master (161818c) will increase coverage by 0.17%.
The diff coverage is 96.26%.

@@            Coverage Diff             @@
##           master     #254      +/-   ##
==========================================
+ Coverage   97.16%   97.34%   +0.17%     
==========================================
  Files         196      195       -1     
  Lines       20214    20403     +189     
==========================================
+ Hits        19641    19861     +220     
+ Misses        573      542      -31     

Flag	Coverage Δ
unittests	97.34% <96.26%> (+0.17%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
tests/test_conf_gen.py	100.00% <ø> (ø)
tests/test_methods.py	100.00% <ø> (ø)
tests/test_plotting.py	100.00% <ø> (ø)
tests/test_hessian.py	98.59% <83.33%> (ø)
autode/utils.py	95.45% <91.86%> (-0.59%)	⬇️
tests/test_utils.py	96.94% <97.84%> (+0.43%)	⬆️
autode/__init__.py	100.00% <100.00%> (ø)
autode/config.py	100.00% <100.00%> (ø)
autode/conformers/conformers.py	100.00% <100.00%> (ø)
autode/constraints.py	98.70% <100.00%> (ø)
... and 19 more

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[t-young31]

Thanks 😄