fix hardcoded scatter marker size issue #54204

Author: tarsur909

doc/source/getting_started/intro_tutorials/04_plotting.rst

@@ -108,7 +108,7 @@ I want to visually compare the :math:`NO_2` values measured in London versus Par
    :okwarning:
 
     @savefig 04_airqual_scatter.png
-    air_quality.plot.scatter(x="station_london", y="station_paris", alpha=0.5)
+    air_quality.plot.scatter(x="station_london", y="station_paris", s = 20, alpha=0.5)
     plt.show()
 
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