Update the binding inheritance tests for the new moment bindings approach

Now that navigation bindings don't pollute the whole widget hierarchy any
more some of these tests can be tidied up.

tests/test_binding_inheritance.py

@@ -47,9 +47,8 @@ async def test_just_app_no_bindings() -> None:
 # An application with a single alpha binding.
 #
 # Sticking with just an app and the default screen: this configuration has a
-# BINDINGS on the app itself, and simply binds the letter a -- in other
+# BINDINGS on the app itself, and simply binds the letter a. The result
-# words avoiding anything to do with movement keys. The result should be
+# should be that we see the letter a, ctrl+c, and nothing else.
-# that we see the letter a, ctrl+c, and nothing else.
 
 
 class AlphaBinding(App[None]):
@@ -114,22 +113,13 @@ class AppWithScreenThatHasABinding(App[None]):
 async def test_app_screen_with_bindings() -> None:
     """Test a screen with a single key binding defined."""
     async with AppWithScreenThatHasABinding().run_test() as pilot:
-        # The screen will contain all of the movement keys, because it
-        # inherits from Widget. That's fine. Let's check they're there, but
-        # also let's check that they all have a non-priority binding.
-        assert all(
-            pilot.app.screen._bindings.get_key(key).priority is False
-            for key in MOVEMENT_KEYS
-        )
-        # Let's also check that the 'a' key is there, and it *is* a priority
-        # binding.
         assert pilot.app.screen._bindings.get_key("a").priority is True
 
 
 ##############################################################################
 # A non-default screen with a single low-priority alpha key binding.
 #
-# As above, but because Screen sets akk keys as high priority by default, we
+# As above, but because Screen sets all keys as high priority by default, we
 # want to be sure that if we set our keys in our subclass as low priority as
 # default, they come through as such.
 
@@ -152,13 +142,7 @@ class AppWithScreenThatHasALowBinding(App[None]):
 async def test_app_screen_with_low_bindings() -> None:
     """Test a screen with a single low-priority key binding defined."""
     async with AppWithScreenThatHasALowBinding().run_test() as pilot:
-        # Screens inherit from Widget which means they get movement keys
+        assert pilot.app.screen._bindings.get_key("a").priority is False
-        # too, so let's ensure they're all in there, along with our own key,
-        # and that everyone is low-priority.
-        assert all(
-            pilot.app.screen._bindings.get_key(key).priority is False
-            for key in ["a", *MOVEMENT_KEYS]
-        )
 
 
 ##############################################################################