DOC/gallery example "Cross section": Fix typo (#3658)

Author: yvonnefroehlich

examples/gallery/images/cross_section.py

@@ -37,7 +37,7 @@
 
 # Add a colorbar for the elevation
 fig.colorbar(
-    # Place the colorbar inside the plot (lower-case "j") in the Botton Right (BR)
+    # Place the colorbar inside the plot (lower-case "j") in the Bottom Right (BR)
     # corner with an offset ("+o") of 0.7 centimeters and 0.3 centimeters in x or y
     # directions, respectively; move the x label above the horizontal colorbar ("+ml")
     position="jBR+o0.7c/0.8c+h+w5c/0.3c+ml",