Fix typo in error message

[stephanie-eng]

Small typo fix

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (f9f1804) 50.50% compared to head (772e748) 50.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2286      +/-   ##
==========================================
- Coverage   50.50%   50.50%   -0.00%     
==========================================
  Files         386      386              
  Lines       31736    31736              
==========================================
- Hits        16026    16025       -1     
- Misses      15710    15711       +1     

Files Changed	Coverage Δ
moveit_core/robot_model/src/robot_model.cpp	74.64% <0.00%> (ø)

... and 1 file with indirect coverage changes

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