BUG: fix typo introduced in function call

[jcrivenaes]

Closes #973

[codecov-commenter]

Codecov Report

Merging #975 (f12fdae) into main (013dc03) will not change coverage.
Report is 2 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #975   +/-   ##
=======================================
  Coverage   80.30%   80.30%           
=======================================
  Files          92       92           
  Lines       13494    13494           
  Branches     2227     2227           
=======================================
  Hits        10837    10837           
  Misses       1930     1930           
  Partials      727      727           

Files	Coverage Δ
src/xtgeo/grid3d/grid_property.py	85.05% <ø> (ø)

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[mferrera]

We double worked this, sorry -- but the type hint and doc string update are still appropriate