DOC: Fix "triangles_height" to "triangle_height" in docs of Figure.colorbar (#4368)

Fix typo in parameter name

Author: yvonnefroehlich

pygmt/src/colorbar.py

@@ -214,9 +214,9 @@ def colorbar(  # noqa: PLR0913
         and **F** entries in the CPT. If no such entries exist, then the system default
         colors for **B** and **F** are used instead (:gmt-term:`COLOR_BACKGROUND` and
         :gmt-term:`COLOR_FOREGROUND`).
-    triangles_height
-        Height of the triangles for back- and foreground colors [Default is half
-        of the bar width].
+    triangle_height
+        Height of the triangles for back- and foreground colors [Default is half of the
+        bar width].
     move_text
         Move text (annotations, label, and unit) to opposite side. Accept a sequence of
         strings containing one or more of ``"annotations"``, ``"label"``, and