[prefix][plotters][user][scatter] Fix default values type

Type is float64 so default value should be numerical.

beat/core/test/prefix/plotters/user/scatter/1.json

@@ -18,12 +18,12 @@
       "description": "The title for this plot"
     },
     "xaxis_multiplier": {
-      "default": "1.0",
+      "default": 1.0,
       "type": "float64",
       "description": "The multiplication factor for the X-axis (horizontal)"
     },
     "yaxis_multiplier": {
-      "default": "1.0",
+      "default": 1.0,
       "type": "float64",
       "description": "The multiplication factor for the Y-axis (vertical)"
     },