Change a couple of more additional occurences of pointer over (#3368)

* Switch two more occassions of "mouse" to "pointer"

* Minor linguistic improvement

doc/user_guide/interactions.rst

@@ -357,7 +357,7 @@ via mouse actions. By default, points are selected on click:
     point = alt.selection_point()
     make_example(point)
 
-By changing some arguments, we can select points on pointerover rather than on
+By changing some arguments, we can select points when hovering over them rather than on
 click. We can also set the ``nearest`` flag to ``True`` so that the nearest
 point is highlighted:
 

doc/user_guide/transform/pivot.rst

@@ -50,7 +50,7 @@ values on multiple lines:
    base = alt.Chart(source).encode(x='date:T')
    columns = sorted(source.symbol.unique())
    selection = alt.selection_point(
-       fields=['date'], nearest=True, on='pointerover', empty=False, clear='mouseout'
+       fields=['date'], nearest=True, on='pointerover', empty=False, clear='pointerout'
    )
 
    lines = base.mark_line().encode(y='price:Q', color='symbol:N')

tests/examples_arguments_syntax/selection_zorder.py

@@ -15,7 +15,7 @@
 
 cars = data.cars.url
 
-hover = alt.selection_point(on='mouseover', nearest=True, empty=False)
+hover = alt.selection_point(on='pointerover', nearest=True, empty=False)
 
 chart = alt.Chart(cars, title='Selection obscured by other points').mark_circle(opacity=1).encode(
     x='Horsepower:Q',