docs: change fig to canvas to reflect new API (#91)

* docs: change fig to canvas to reflect new API

Author: jcharkow

docs/Parameters/basePlot.tsv

@@ -9,7 +9,7 @@ height		int	Height of plot, units dependent on backend.
 width		int	Width of plot in pixels, units dependent on backend.
 grid	False	bool	Whether to show grid on the plot
 toolbar_location	“above”		Location of toolbar for interactive plots. One of: [“above”, “below”, “left”]
-fig	None	fig	Existing Figure object to plot on
+canvas	None	matplotlib.axes | bokeh.figure | plotly.graph_objects.Figure 	Existing Figure object to plot on
 xlabel	None	str	Label for x axis
 ylabel 	None	str	Label for y axis
 show_plot	True	bool	Whether to display the plot. If plot is not shown, will return the plot object corresponding with the backend. If plot is displayed the method returns None