[BUG] in LibffmConverter docstrings

[miguelgfierro]

Description

fix #1577

Related Issues

Checklist:

• I have followed the contribution guidelines and code style for this project.
• I have added tests covering my contributions.
• I have updated the documentation accordingly.
• This PR is being made to staging branch and not to main branch.

[codecov-commenter]

Codecov Report

Merging #1589 (9cf8d82) into staging (7013f0d) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           staging    #1589      +/-   ##
===========================================
+ Coverage    61.88%   61.90%   +0.01%     
===========================================
  Files           84       84              
  Lines         8458     8462       +4     
===========================================
+ Hits          5234     5238       +4     
  Misses        3224     3224              

Flag	Coverage Δ
pr-gate	61.90% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
recommenders/datasets/pandas_df_utils.py	94.89% <ø> (ø)
recommenders/models/rbm/rbm.py	73.66% <100.00%> (+0.47%)	⬆️

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[miguelgfierro]

FYI @anargyri