Fix docstring in plotgrid

[DanielVandH]

The newline meant ?plotgrid didn't show the docstring

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.47%. Comparing base (d243564) to head (abdcdd5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #189   +/-   ##
=======================================
  Coverage   90.47%   90.47%           
=======================================
  Files          11       11           
  Lines         819      819           
=======================================
  Hits          741      741           
  Misses         78       78           

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