[system][plotters][scatter] Fix default parameters

They were containing wrong keys.

system/plotters/plot_username/scatter/default_plotterparameter.txt

-{ "grid": true, "title-fontsize": 12, "legend-loc": "best", "width": 800, "height": 600, "dpi": 120, "legend-fontsize": 8, "axis-fontsize":10 }
+{
+  "grid": true,
+  "width": 800,
+  "height": 600,
+  "dpi": 120
+}