Fix typo in Forestplot

[hectormz]

Description

• This PR fixes a type where Forestplot was written as Forestpĺot in comments, which showed up in online documentation.

Checklist

• Changes are listed in changelog

[codecov]

Codecov Report

Merging #1937 (2a20673) into main (6e0cc28) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1937   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files         116      116           
  Lines       12362    12362           
=======================================
  Hits        11339    11339           
  Misses       1023     1023           

Impacted Files	Coverage Δ
arviz/plots/forestplot.py	94.59% <ø> (ø)

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[OriolAbril]

Thanks!