docs(guide/controller): change "hides" to "shadows"

"Shadows" should better convey the meaning of "overwriting the value of the property in the child
scope, while leaving the parent scope intact".
"Hides" could give the impression that it makes the property unavailable in the child scope and
leaving "overrides" only, could give the impression that the parent scope would be affected too,
especially to people not familiar with JavaScript's prototypal inheritance.

Closes #15375

Author: kentwalters

docs/content/guide/controller.ngdoc

@@ -253,10 +253,10 @@ scopes being created for our view:
 
 - The root scope
 - The `MainController` scope, which contains `timeOfDay` and `name` properties
-- The `ChildController` scope, which inherits the `timeOfDay` property but overrides (hides) the `name`
-property from the previous
-- The `GrandChildController` scope, which overrides (hides) both the `timeOfDay` property defined in `MainController`
-and the `name` property defined in `ChildController`
+- The `ChildController` scope, which inherits the `timeOfDay` property but overrides (shadows) the
+  `name` property from the previous scope
+- The `GrandChildController` scope, which overrides (shadows) both the `timeOfDay` property defined
+  in `MainController` and the `name` property defined in `ChildController`
 
 Inheritance works with methods in the same way as it does with properties. So in our previous
 examples, all of the properties could be replaced with methods that return string values.